PHYSIOLOGY 


AND 


HYGIENE 


CALIFORNIA 
STATE  SERIES 


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PHYSIOLOGY   AND   HYGIENE 


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COPYRIGHT,  1906,  BY 
THE  PEOPLE  OF  THE  STATE  OF  CALIFORNIA 

COPYRIGHT,  1902,  BY 
BUEL  P.   COLTON 

In  the  compilation  of  this  book  certain  matter  from  an  Elementary 
Physiology  and  Hygiene  by  Buel  P.  Colton  has  been  used.  All  such 
matter  is  protected  by  the  copyright  entries  noted  above. 


-  .,,.  .. 

-H 

L'DUGAXiOW  DEPT. 


PREFACE. 

IN  preparing  this  work  for  younger  students  especial 
pains  have  been  taken  to  niake  it  clear  and  simple.  Sen- 
tences, paragraphs,  and  chapters  have  been  made  short, 
and  a  concise  summary  follows  each  chapter.  So  far  as 
possible  technical  terms  have  been  avoided  and  English 
words  preferred  to  Latin,  for  instance,  post-caval  vein 
instead  of  vena  cava  inferior,  spinal  bulb  instead  of  medulla 
oblongata,  etc.  The  Latin  form  of  the  plural  puzzles  the 
student  who  has  not  had  Latin ;  hence  the  English  form 
of  the  plural  is  used,  as  pleuras,  ganglions,  ciliums,  ml- 
/uses,  papillas,  etc. 

The  illustrations  are  made  clear  and  distinct,  and  are 
labeled  directly ;  that  is,  the  detail  labels  are  on,  or  very 
close  to,  the  part  labeled,  so  that  time  and  effort  are 
not  needed  to  associate  the  thing  and  the  name.  A  large 
number  of  the  illustrations  are  original. 

A  few  simple  experiments  are  given ;  for  although  much 
less  can  be  done  than  with  older  students,  yet  considerable 
must  be  done  if  the  subject  is  to  be  made  clear. 

The  subject  of  hygiene  has  received  careful  attention; 
for  it  must  not  be  forgotten  that  the  main  object  of  this 
study  is  that  each  pupil  may  learn  how  to  take  better  care 
of  his  own  body.  It  has  been  the  aim  not  to  give  mere 
•arbitrary  rules  of  health,  to  be  blindly  and  implicitly  fol- 
lowed, but  to  base  all  precepts  of  hygiene  on  the  general 
principles  of  physiology,  so  that  the  pupil  may  understand 

f/55976 


iv  Preface. 

the  why  and  the  how  so  far  as  possible.  His  obedience 
will  be  more  ready  and  more  complete  when  based  on 
intelligence  than  when  it  is  simply  a  submission  to  a 
peremptory  command.  In  many  cases,  too,  the  general 
principle  will  serve  as  a  guide  where  no  rule  has  been  laid 
down ;  no  treatise  can  cover  all  possible  contingencies. 

At  the  end  of  the  book  is  a  glossary  in  which  all  tech- 
nical terms  are  pronounced  and  explained. 


CONTENTS. 


CHAPTER  PAGE 

I.     Introduction I 

II.     The  Bones 5 

III.  Muscles  and  Motion .16 

IV.  The  Muscles  and  the  Bones .28 

V.  The  Nervous  System  —  Sensation  and  Motion       ...       36 

•  VI.     Circulation  of  the  Blood -47 

VII.     Control  of  Circulation .       67 

VIII.     The  Blood  and  the  Lymph 74 

IX.     External  Respiration 83 

X.     Internal  Respiration 97 

XI.  Ventilation  and  Heating        .......     106 

XII.     Dust  and  Bacteria 114 

XIII.  Excretion 123 

XIV.  Foods  and  Cooking 134 

XV.  The  Digestive  System  —  Digestion  in  the  Mouth  .         .         .     146 

XVI.     Digestion  in  the  Stomach 156 

XVII.     Digestion  in  the  Intestine 164 

XVIII.     Absorption 172 

XIX.     Hygiene  of  Digestion  —  Nutrition 181 

XX.     Exercise  and  Bathing 192 

XXI.     The  Brain .         .198 

XXII.  The  Senses  —  The  Gerieral  Senses  —  Touch  and  Temperature 

Sense 208 

XXIII.  The  Sense  of  Sight        .         .        .         .         .  .         .215 

XXIV.  Defects  of  Eyesight  and  Care  of  the  Eyes      .         .         .         .223 
XXV.     Taste,  Smell,  Hearing,  and  the  Voice 233 

XXVI.  Accidents  —  What  to  do  till  the  Doctor  comes       .         .         .     240 

XXVII.     Vaccination 250 

XXVIII.     Stimulants  and  Narcotics 253 

GLOSSARY 261 

INDEX     .  273 

v 


TO   THE   TEACHER. 

IT  is  not  the  fault  of  the  teacher  that  the  human  body  is  very  com- 
plex in  structure  and  that  many  of  the  functions  are  obscure.  Never- 
theless the  teacher  is  responsible  for  making  the  subject  as  clear  as  is 
possible.  To  do  this  it  is  absolutely  essential  to  perform  some  experi- 
ments and  to  show  some  of  the  internal  organs  of  such  an  animal  as 
the  rabbit,  or  materials  obtained  from  the  butcher.  This  involves 
work,  and  sometimes  work  that  is  not  altogether  pleasant.  But  no 
earnest  teacher  will  shrink  from  work  simply  because  it  is  not  agreeable. 

Every  school  should  have  a  microscope,  by  means  of  which  to  show 
the  corpuscles  of  the  blood,  cells  from  various  tissues,  the  circulation 
of  blood  in  a  frog's  web,  or  in  the  gills  of  a  tadpole.  From  various 
dealers  in  school  supplies  there  can  be  purchased  mounted  slides  illus- 
trating most  of  the  kinds  of  cells  and  tissues  of  the  body.  These  can 
be  successfully  used  by  teachers  who  have  not  had  the  advantages  of  a 
thorough  training  in  histology. 

When  studying  the  bones  the  teacher  can  usually  borrow  some 
human  bones  from  the  nearest  physician.  Also  get  a  femur  of  a  horse 
or  cow  and  saw  it  in  two  lengthwise.  It  will  show  the  structure  as 
well  as  a  human  femur.  It  is  easy  to  test  the  composition  of  bone  by 
burning  and  by  acid.  Corned  beef  shows  well  the  structure  of  muscle. 
A  sheep  shank  from  the  butcher  may  be  used  to  show  the  joints, 
synovia,  cartilage,  ligaments,  etc.  Most  pupils  will  be  ready  to  help 
dissect  a  heart  and  will  be  delighted  to  see  the  action  of  the  valves. 

By  means  of  a  common  bulb  syringe  and  a  little  glass  and  rubber 
tubing  the  action  of  the  arteries  and  the  nature  of  the  pulse  and  capil- 
lary flow  may  be  illustrated.  The  circulation  of  blood  in  the  web  of  a 
frog's  foot  is  such  an  interesting  and  instructive  sight  that  the  teacher 
should  show  it  to  the  class  without  fail.  Even  if  the  school  has  no 
microscope  and  the  teacher  without  experience,  it  is  often  possible  to 
get  a  near-by  physician  to  show  it  to  the  class.  The  coagulation  of  the 
blood  is  readily  shown.  The  experiments  illustrating  the  action  of  the 

vii 


viii  To  the  Teacher. 

diaphragm  are  very  helpful,  and  any  teacher  possessing  a  modicum  of 
ingenuity  and  willingness  to  work  can  prepare  them.  In  addition  to 
the  experiments  given  in  illustration  of  the  chemistry  of  respiration,  it 
is  desirable  to  show  nitrogen  and  the  composition  of  the  air.  This  can 
readily  be  accomplished  by  following  the  directions  in  the  larger  book 
or  in  any  chemistry. 

To  learn  the  temperature  of  the  body  borrow  a  clinical  thermometer 
from  a  physician.  Have  the  children  make  little  paper  windmills  to 
show  the  air  currents  in  rooms,  over  stoves,  registers,  radiators,  etc. 
The  children  should  test  the  currents  of  air  at  all  gratings  and  registers 
in  the  schoolroom  by  holding  a  handkerchief  up  close  to  them.  The 
teacher  should  place  a  board  under  a  window  (as  directed  in  this  book) 
to  show  how  to  ventilate  a  room  without  unpleasant  drafts.  Each 
pupil  should  prepare  a  section  of  tooth  as  directed  in  this  book.  When 
studying  the  subject  of  absorption,  the  teacher  should  get  from  the 
butcher  about  a  foot  of  the  small  intestine  of  a  calf.  He  will  wash  it 
clean  for  a  small  consideration.  Cut  this  into  pieces  an  inch  long. 
Turn  them  inside  out  and  place  them  in  shallow  dishes  of  water.  The 
villuses  will  readily  be  seen.  A  piece  of  the  gullet  will  show  the  mus- 
cular and  mucous  coats.  Have  the  pupils  make  a  careful  study  of 
Fig.  87  and  also  of  Figs.  85  and  86,  which  are  designed  to  lead  up  to 
Fig.  87.  If  the  teacher  is  willing  to  practice,  he  can  soon  learn  to 
demonstrate  muscle''  action  by  means  of  frog's  muscle  and  to  show 
reflex  action  of  the  spinal  cord  with  a  frog. 

Many  interesting  experiments  on  the  senses  can  be  made  with  chil- 
dren, such  as  the  test  of  touch  with  compass  points,  keenness  of  sight, 
hearing,  accuracy  of  the  muscular  sense,  etc.  The  internal  structure 
of  the  eye  never  fails  to  awake  enthusiasm,  and  the  teacher  should 
show  this,  and  perhaps  some  of  the  pupils  can  also  succeed  in  doing 
the  same.  If  the  teacher  can  obtain  a  book  on  nursing,  or,  better  still, 
persuade  a  physician  or  trained  nurse  to  come  before  the  class,  they 
can  learn  how  to  prepare  and  apply  bandages,  to  dress  wounds,  to  treat 
for  drowning,  etc. 


ELEMENTARY   PHYSIOLOGY. 


CHAPTER  I.        ;    -  »*-';:•*: 
INTRODUCTION. 

The  Care  of  a  Machine.  —  In  order  to  take  good  care  of 
a  machine  one  must  know  about  its  different  parts,  what 
each  part  is  to  do,  and  the  relation  of  the  parts  to  one 
another.  He  must  keep  the  machine  clean  and  well  oiled, 
and  must  not  overwork  it.  Otherwise  it  will  neither  do 
good  work  nor  last  long.  This  is  true  not  only  of  machines 
like  typewriters  and  sewing-machines,  but  of  bicycles,  and 
even  of  such  simple  tools  as  knives  and  scissors.  We 
would  not  trust  the  management  of  any  valuable  machine 
to  one  who  did  not  know  enough  to  take  good  care  of  it. 

The  Care  of  the  Body.  —  The  care  of  the  body  is  of  vastly 
greater  importance.  We  can  get  new  parts  to  replace 
those  worn  out  in  a  machine.  While  we  can  get  artificial 
limbs,  we  cannot  replace  such  organs  as  an  eye,  the  heart, 
or  the  lungs.  If  we  do  not  take  good  care  of  our  bodies, 
we  cannot  keep  well,  live  long,  or  do  good  work.  So  we 
need  to  know  about  the  different  parts  of  our  bodies,  the 
work  that  each  is  to  do,  and  the  relation  of  the  parts  to 
each  other. 

This  knowledge  is  desirable  for  everybody ;  but  espe- 
cially necessary  for  those  who  live  a  quiet,  indoor  life.  In- 
door people  do  not  get  as  much  exercise  or  as  much  fresh 

i 


2  Physiology. 

air  as  those  who  live  outdoors.  An  indoor  life  is  always 
more  or  less  artificial,  and  we  need  to  take  especial  care 
that  our  bodies  do  not  suffer.  It  is  believed  that  one 
seventh  of  the  deaths  among  civilized  races  are  due  to  lung 
troubles.  Those  who  live  outdoors  have  little  trouble  of 
such  kind.  We  need  to  learn  about  the  air  and  breathing, 
about  exercise  and  bathing,  about  food  and  digestion,  about 
blood  and  its  circulation,  about  the  nervous  system,  etc. 

Hygiene. ; —  Hygiene  is  the  art  of  preserving  the  health. 
This  is  the  main  object  of  our  study  of  this  subject. 

Physiology.  —  Physiology  is  the  science  of  the  action  of 
the  body  and  its  various  parts.  We  must  know  the  natural 
action  of  the  parts  of  the  body  to  be  able  to  keep  them  in 
good  working  order. 

Organ.  —  An  organ  is  any  part  of  the  body  that  has  a 
special  work  to  do,  as  the  hand,  eye,  or  heart. 

Function.  —  The  work  or  action  of  an  organ  is  its 
function. 

Anatomy. — Anatomy  is  the  science  of  structure.  We 
need  to  know  something  of  the  structure  of  our  bodies. 
For  this  purpose  we  may  study  the  internal  structure  of 
the  sheep,  pig,  calf,  and  rabbit  —  which  is  very  similar  to 
our  own.  We  can  take  the  hearts,  lungs,  brains,  eyes,  and 
muscles  of  such  animals  to  learn  something  of  the  struc- 
ture of  these  organs  in  our  own  bodies  ;  if  we  fail  to  do  this, 
we  can  never  get  a  clear  understanding  of  the  subject. 

Tissues.  —  Every  organ  is  made  up  of  several  different 
kinds  of  material.  For  instance,  in  a  slice  across  a  ham 
we  see  skin  on  the  outside,  then  fat  meat,  lean  meat,  and 
bone.  These  "  primary  building  materials "  of  the  body 


Introduction.  3 

are  called  tissues.  A  tissue  is  a  collection  of  similar  cells 
devoted  to  the  same  work;  or,  in  other  words,  a  tissue 
is  a  set  of  cells  having  the  same  structure  and  the  same 
function.  Thus  we  have  muscular  tissue,  nervous  tissue, 
bony  tissue,  etc. 

Cells.  —  The  whole  body  is  made  up  of  small  parts,  called 
cells,  which  are  to  be  compared  to  the  bricks  in  a  house. 
These  cells  are  of  various  shapes  in  the  different  tissues. 
The  living  material  of  the  body  is  called  protoplasm.  It  is 
a  jelly-like  substance  resembling  the 
white  of  an  egg,  though  often  pre- 
senting a  dotted  appearance.  A  cell, 
in  its  simplest  form,  is  merely  a  dis- 
tinct particle  of  protoplasm.  Each  Nucleus 
cell  usually  has,  however,  a  more  Fig.  i.  Epithelial  ceils  from 

J  .  .  the  Inside  of  the  Cheek. 

dense  central  part,  called  the  nucleus. 

The  great  majority  of  cells  have  a  distinct  covering  or 
cell-wall.  A  grape  or  cherry  serves  very  well  to  illustrate 
a  cell.  The  skin  represents  the  cell-wall,  the  pulp  corre- 
sponds to  the  protoplasm,  and  the  seed  to  the  nucleus. 
(See  Fig.  39,  Cells  of  the  Epidermis.) 

Division  of  Labor  in  a  Community.  —  We  are  all  aware 
of  the  advantages  of  division  of  labor  in  a  community.  If 
each  person  learns  to  do  one  thing  well,  all  can  work 
together  economically  for  the  common  good,  time  is  saved, 
and  cheaper  and  better  goods  are  produced. 

Division  of  Labor  in  the  Body.  —  In  the  body  there  is  a 
division  of  labor  similar  to  that  in  a  community.  In  the 
first  place  each  organ  has  its  special  work,  and  the  various 
organs  act  helpfulty  together,  each  working  for  all  the  rest 
and  worked  for  by  them. 


4  Physiology. 

The  general  structure  of  all  the  cells  is  about  the  same, 
yet  they  differ  enough  for  us  to  tell  them  apart.  They 
differ  more  in  their  work  than  in  their  appearance.  Each 
has  some  one  kind  of  work  that  it  can  do  well,  and  to 
which  it  devotes  itself.  The  nerve  cells  receive  impressions 
from  the  outer  world,  carry  nerve  currents,  and  control  the 
various  actions  of  the  body.  The  muscle  cells  have  as 
their  work  the  production  of  motion. 

The  Life  of  Cells.  —  Each  cell  must  take  food  for  itself 
and  grow.  Each  has  a  birth,  life,  and  death,  as  each  indi- 
vidual in  a  community  of  men ;  and  as  the  community 
continues,  while  the  individual  members  are  constantly 
changing,  so,  in  the  body,  while  the  form  remains  about 
the  same  from  year  to  year  (in  the  adult),  the  cells  are 
continually  changing,  some  dying,  and  others  taking  their 
places.  Thus  it  is  seen  that  though  the  cells  are  packed 
closely  together  and  though  they  work  in  groups,  each  cell 
leads,  in  one  sense,  an  independent  life.  Like  the  indi- 
vidual in  the  community,  each  lives  for  itself,  yet  all  work 
together  for  the  common  good. 


CHAPTER  II, 
THE  BONES, 

The  Two  Parts  of  a  Skeleton.  —  The  skeleton  consists  of 
two  portions,  (i)  the  central  axis,  or  spinal  column,  to 
which  the  head  belongs;  and  (2)  the  limbs  and  the  bones 
belonging  to  them. 

The  Uses  of  the  Bones.  —  i .  The  skeleton  gives  the  form 
to  the  body. 

2.  It  supports  the  softer  tissues. 

3.  It  protects  softer  parts,  as  the  brain  in  the  skull,  the 
spinal  cord  in  the  spinal  column,  the  heart  and  lungs  in 
the  chest,  etc. 

4.  The  bones  serve  as  levers  in  producing  motion  and 
locomotion. 

Study  of  a  Vertebra.  —  Take  a  vertebra  from  the  middle  of  the  spinal 
column :  — 

1.  Its  most  solid  part  is  its  body. 

2.  On  the  dorsal  side  of  this  is  the  neural  arch,  forming  with  the 
body  the  neural  ring,  through  which  the  spinal  cord  passes. 

3.  From  this  arch  there  extend  projections,  or  processes.     Hold  the 
vertebra  by  the  tip  of  its  longest  process,  and  place  it  beside  the  cor- 
responding vertebra  in  the  complete  skeleton.     Note  that :  — 

(a)  The  body  is  flattened  where  it  fits  against  the  vertebras  above 
and  below  it ; 

(£)  The  holes  in  the  vertebras  form  a  passage  for  the  spinal  cord ; 

(c}  The  middle  projection  is  the  spinous  process,  and  the  series  of 
spinous  processes  form  the  ridge  of  the  backbone ; 

(d)  The  two  side  projections  are  the  transverse  processes. 

5 


6  Physiology. 

Fit  together  two  vertebras  in  their  proper  order  and  observe  that :  — 
(e)  The  openings  at  the  sides,  through  which  the  spinal  nerves  pass, 
are  iormed  by  notches,  or  grooves,  in  the  two  vertebras. 


Neural  Arch 


Body 


Transverse  Process 


..Spinous  Process 


Neural  Ring 
Fig.  2.    Upper  View  of  Thoracic  Vertebra. 


Demi-facet  for  Head  of  Rib 


Body 


Anterior  Articular 
Process 


Facet  for  Tubercle  ot 
Rib 


X  Transverse  Process 


...Spinous  Process 


Fig.  3.    Left  Side  View  of  Thoracic  Vertebra. 

(/)  The  two  projections  extending  upward  from  the  ring  of  one 
vertebra  fit  against  two  projections  extending  downward  from  the  other 
vertebra.  These  are  the  anterior  and  posterior  articular  processes. 


The  Spinal  Column.  —  The  central  part  of  the  skeleton 
is   the  backbone,  or  spinal  column^     As  a  whole  it  is  a 


The  Bones.  7 

column,  widening  toward  the  base,  composed  of  a  series  of 
separate  bones  called  vertebras. 

Each  vertebra  has  seven  projections,  four  for  joining 
other  vertebras  (two  upper  and  two  lower),  two  side,  and 
one  spinous. 

Hole  for  Blood  Tubes   f&^lfiM&K^  Anterior  Articular-  Facet 

Neural  Arch 


Body _ 

Spinous  Process 


X\ Neural  Ring 


Fig.  4.    Upper  View  of  Cervical  Vertebra. 


Body 


Spinous  Process 
Fig.  5.    Left  Side  View  of  Cervical  Vertebra. 

How  the  Vertebras  Fit  Together.  —  The  smooth  places 
where  the  projections  join  are  called  facets.  Observe  on 
each  side  of  the  body  of  the  vertebra  a  facet  where  the 
head  of  the  rib  joined  it.  There  is  also  a  facet  on  the  side 
process  where  the  side  of  the  rib  joined  it. 

The  Cervical  Vertebras.  —  The  seven  cervical  (neck) 
vertebras  have  holes  through  their  side  projections  for  the 
passage  of  blood  tubes. 


8 


Physiology. 


FLAT  BONES  OF  THE  SKULL. 

r-THE  CRANIUM, 


NASAL  BONES 


J-MALAR  (CHEEK)  BONE. 
•-SUPERIOR  MAXILLARY  BONES 
-INFERIOR  MAXILLARY  BONE 
•SPINAL  COLUMN. CERVICAL  REGION* 


SHOULDER  BLADE  - 


Fig.  6.    Side  View  of  the  Human  Skeleton. 


The  Bones. 


TABLE  OF  THE  BONES. 


HEAD  (28) 


Skull  (8) 


Face  (14) 


Ears  (6) 


CERVICAL  REGION  (8) 


THORAX  (37, 


UPPER  EXTREMITIES  (64) 


LUMBAR  REGION  (5) 
PELVIS  (4) 


Frontal  (forehead). 

2  Temporal  (temples). 

2  Parietal  (side). 

Occipital  (posterior  base). 

Sphenoid  (base). 

Ethmoid  (base  of  nose  and  between  eyes), 

2  Superior  Maxillas(  upper  jaw). 

2  Nasal  (bridge  of  nose). 

2  Malar  (cheek). 

2  Lachrymal  (inner  front  corner  of  orbit). 

2  Turbinated  (within  nostrils). 

2  Palate  (posterior  hard  palate). 

Vomer  (nasal  partition). 

Inferior  Maxilla  (lower  jaw). 

(Malleus  (hammer). 
Stapes  (stirrup). 
Incus  (anvil). 


{7  Cervical  Vertebras  (neck). 
Hyoid  Bone  (base  of  tongue). 

{14  True,  6  False,  4  Floating  Ribs. 
12  Thoracic  Vertebras  (back)  . 
Sternum. 

c,     ,,      /Clavicle  (collar-bone). 

ier"  \  Scapula  (shoulder-blade). 
f  Humerus  (arm). 

Arm- 


Hand. 


8  Carpal  (wrist). 

5  Metacarpal  (palm). 

14  Phalanges  (fingers). 


5  Lumbar  Vertebras  (loins). 

(  2  Innominates. 
<  Sacrum. 
I  Coccyx. 


LOWER  EXTREMITIES  (60) 


Thigh. 
Leg. 


Foot. 


Femur. 

[  Patella  (knee-pan). 
i  Tibia  (large  bone). 
v  Fibula  (outer  bone), 
r  7  Tarsal  (instep,  heel). 
\  5  Metatarsal  (arch). 
I  14  Phalanges  (toes). 


2 — PHY 


io  Physiology. 

Atlas  and  Axis.  —  The  first  vertebra,  the  atlas,  has  no 
body.  The  second  vertebra  is  the  axis.  It  has  a  peg 
which  runs  up  into  the  atlas.  In  shaking  the  head,  the 
atlas,  with  the  head,  turns  on  this  peg  of  the  axis.  In 
nodding  the  head,  the  head  simply  rocks  back  and  forth 
on  the  atlas. 

The  Thoracic  Vertebras.  —  The  twelve  rib-supporting 
vertebras  are  the  thoracic  vertebras. 

The  Lumbar  Vertebras.  —  The  next  five  are  the  lumbar. 

The  Sacrum  and  Coccyx.  —  The  sacrum  is  composed  of 
five  vertebras  grown  together,  and  the  remaining  four  are 
combined  in  the  coccyx. 

Review  of  the  Spinal  Column.  —  Let  the  eye  slowly  re- 
view the  whole  spinal  column,  noting  in  what  points  the 
vertebras  are  all  alike.  Note  also  their  differences. 

Flexibility  of  the  Spinal  Column.  —  In  well-prepared 
skeletons  there  are  pads  of  felt  which  take  the  place  of  the 
layers  of  cartilage  that  were  between  the  vertebras.  These 
cartilages  are  tough  and  elastic,  and  firmly  attached  to  the 
vertebras  above  and  below.  They  serve  both  to  keep  the 
vertebras  apart  and  to  hold  them  together.  When  we  bend 
the  shoulders  to  the  right,  the  right  edges  of  these  carti- 
lages are  compressed,  and  the  left  edges  are  stretched,  as 
a  piece  of  india  rubber  would  be  if  it  were  glued  be- 
tween the  ends  of  two  spools,  and  the  whole  were  slightly 
bent.  The  cartilages  also,  by  their  elasticity,  protect 
the  brain  from  the  shock  it  would  receive  in  jumping, 
walking,  etc. 

Curves  of  the  Spinal  Column. — View  the  spinal  column 
from  the  side.  Draw  a  line  representing  all  its  curves. 


The  Bones. 


II 


The  Cavities  of  the  Skeleton.  —  Examine  the  cavity  of  the  skull.  If 
the  class  has  not  a  skull  which  has  been  sawed  across,  look  into  the 
skuli  cavity  through  the  hole  where  the  spinal  cord  joined  the  brain. 


Neural  Arch 


Transverse  Process 


Body  


Neura!  Ring 
Fig-  7.    Upper  View  of  Lumbar  Vertebra. 


Body 


Transverse 
Process 


Spinous 
Process 


Posterior  Articular  Process 
Fig.  8.    Side  View  of  Lumbar  Vertebra. 

Observe  the  conical  shape  of  the  chest.  In  the  entire  body  the 
bones  and  muscles  about  the  shoulders  usually  make  a  reversed  cone  of 
the  upper  part  of  the  trunk. 

Observe  that  most  of  the  ribs  are  connected  with  the  breastbone  by 
cartilages. 

The  upper  limbs  are  jointed  with  the  body  only  where  the  inner 
ends  of  the  collar  bones  join  the  breastbone. 


1 2  Physiology. 

The  Skeleton  of  a  Cat  or  Rabbit.  —  Examine  the  skeleton  of  a  cat  or 
rabbit  for  the  sake  of  comparison.  Note  especially  the  skull  and  spinal 
column.  This  knowledge  will  aid  in  understanding  the  brain  and 
spinal  cord. 

The  Weight  of  Bones.  —  The  bones  make  about  one  sixth 
of  the  weight  of  the  living  body.  When  dried  they  may 
lose  half  of  their  weight. 

Microscopic  Structure  of  Bone,     i .   Examine  with  a  Hand  Lens.  — 

Hold  a  mounted  cross-section  of  bone  up  to  the  light  and  examine  with 
a  hand  lens.  The  solid  part  of  the  bone  will  be  seen  to  be  pierced  by 
many  small  holes  (or  if  the  holes  are  filled,  they  will  appear  as  black 
spots).  These  are  the  cross-sections  of  the  canals,  through  which  run 
the  blood  tubes,  mainly  lengthwise,  through  the  bone. 

2.  Examine  with  the  Low  Power  of  a  Compound  Microscope. — 
Examine  the  section  under  the  microscope,  using  a  half-inch  objective. 
The  bony  matter  will  now  be  seen  to  be  arranged  in  rings  around  the 
canals,  somewhat  like  the  rings  seen  on  the  end  of  a  log. 

Between  the  rings  are  circles  of  elongated  dark  dots.  These  are 
cavities  in  which  were  the  live  bone-corpuscles  which  built  up  the  bone. 
The  bone  was  at  first  cartilage.  Later,  mineral  matter  was  deposited, 
forming  true  bone. 

3.  Examine  with  a  High  Power.  —  Now  examine  the  section  under  a 
one-fifth-inch  objective.     From  the  dark  cavities  there  run  out,  in  every 
direction,  little  crevices,  appearing  as  fine  black  lines.     Through  the 
haversian  canals,  lacunas,  and  crevices,  the  nourishing  materials  of  the 
blood  reach  all  parts  of  the  bone. 

The  Chemical  Composition  of  Bone. —  i.  Take  a  tall,  narrow  jar,  or 
a  lamp  chimney  corked  at  one  end,  and  nearly  fill  with  water.  Add 
one  sixth  as  much  hydrochloric  acid.  Put  into  this  a  slender,  dry  bone, 
such  as  a  fibula  or  rib.  In  twenty-four  hours  take  it  out,  rinse  it  thor- 
oughly, and  examine  it.  The  acid  will  probably  have  dissolved  out  the 
mineral  matter  and  left  the  animal  matter  so  soft  that  it  may  be  tied 
into  a  knot. 

2.  Lay  a  piece  of  bone  on  a  shovel,  or  piece  of  sheet  iron,  and  place 
in  the  fire.  The  animal  matter  is  burned  out,  leaving  the  brittle  min- 
eral matter* 


The  Bones. 


Composition  of  Bone.  —  Bone  is  composed  of  two  thirds 
mineral  matter  and  one  third  animal  matter ;  in  childhood 
the  animal  matter  is  in  larger  proportion,  while  hi  old  age 
the  mineral  matter  is  in  excess.  The  mineral  matter  is 
chiefly  phosphate  of  lime,  while  the  animal  matter  is 
largely  gelatin. 


Lamellas 


Lacunas 


Canaliculi  Haversian  Canal 

Fig.  9.    Cross-section  of  Bone.     (Highly  Magnified.) 


the 


Classification  of  Joints.  —  i.    Immovable,   such  as 
joints  between  the  bones  of  the  skull  ; 

2.  Mixed,  such  as  the  joints  between  the  vertebras  ; 

3.  Movable,  which  allow  free  motion  between  the  parts; 

(a)  Ball  and  socket,  as  in  the  hip  and  shoulder  ; 

(b)  Hinge,  as  in  the  knee  and  elbow; 

(c)  Pivot,  as  in  the  forearm,  and  between  the  atlas  and 
axis; 


14  Physiology. 

(d)  Gliding,  as  between  the  short  bones  of  the  wrist 
and  of  the  ankle. 

Study  of  Joints.  —  Examine  these  joints  in  the  prepared  skeleton, 
and  so  far  as  possible,  in  sheep  shanks,  or  in  fresh  specimens  of  rabbits. 
Compare  the  ball  and  socket  joints  of  the  hip  and  shoulder.  Also  com- 
pare the  hinge  joints  of  the  knee  and  elbow. 

Hygiene  of  the  Bones.  —  Sometimes  the  bones  of  chil- 
dren are  lacking  in  mineral  matter,  and  are  too  soft  and 
flexible.  This  is  true  in  a  disease  called  rickets.  Even  if 
the  bones  are  natural,  children  should  not  be  encouraged 
to  walk  early,  as  bow-legs  may  result.  Most  bow-legged 
persons  seem  to  be  active,  and  probably  their  muscles 
developed  faster  than  the  bones.  Unnatural  positions  or 
over-use  of  special  groups  of  muscles  may  result  in  lateral 
curvature  of  the  spine.  The  height  of  seats  and  desks 
should  be  carefully  looked  after. 

Sprains  and  Dislocations.  —  Sprains  and  dislocations  are 
injuries  to  the  joints,  and  often  bring  more  serious  results 
than  a  broken  bone.  There  should,  usually,  be  complete 
rest  until  the  part  can  be  used  without  pain.  Otherwise  a 
stiffened  joint  may  result.  Hot  water  applied  to  a  sprain 
or  bruise  with  rubbing  will  reduce  soreness  and  may  pre- 
vent discoloration.  But  if  there  is  inflammation,  cold  water 
should  be  applied.  Bandages  may  be  needed  for  support. 

Broken  Bones.  —  When  a  bone  is  broken,  of  course  a 
physician  should  be  sent  for.  Care  must  be  taken  that  the 
limb  be  kept  straight.  If  this  is  not  done,  the  sharp  ends 
of  the  bone  (see  Fig.  22)  may  cut  or  tear  the  surrounding 
tissues,  or  even  cut  blood  tubes.  So,  if  the  person  must 
be  carried,  it  is  well  to  tie  a  piece  of  board  under  the  limb 
to  keep  from  bending  it.  A  cane,  umbrella,  or  any  light 
rigid  bar  will  serve  for  this  purpose. 


The  Bones.  15 

Summary.  —  I.   The  skeleton  consists  of  the  central  axis  and  the 

limbs. 

2.  Each  vertebra  consists  of  a  body,  ring  (around  spinal  cord),  and 
processes. 

3.  Pads  of  cartilage  connect  the  vertebras. 

4.  Throughout  the  bone  there  are  tubes  and  crevices  through  which 
it  receives  its  nourishment  from  the  blood. 

5.  Bone  consists  of  animal  matter  with  limy  matter  embedded  in  it. 

6.  Sprains  should  be  treated  carefully  to  avoid  stiffened  joints. 

Questions.  —  i.   Why  do  the  bones  of  old  people  break  so  much 
more  easily  than  those  of  children  ? 

2.  What  is  the  use  of  the  central  marrow  ? 

3.  What  is  the  work  of  the  red  marrow  in  the  spongy  ends  of  the 
bones  ? 

4.  What  are  "  sesamoid  "  bones  ? 


CHAPTER   III. 
MUSCLES  AND  MOTION. 

Motion  and  Life. —  Motion  is  one  of  the  surest  signs  of 
life.  While  we  are  sitting  still,  as  we  say,  there  are  fre- 
quent slight  motions  of  the  head,  body,  and  limbs.  Even 
during  sleep  the  movements  of  breathing  maybe  seen;  the 
hand  laid  upon  the  chest  may  feel  the  beating  of  the  heart, 
and  the  finger  detect  the  pulse  in  a  number  of  places.  We 
must  move  to  get  our  food,  or  at  least  to  eat  and  digest  it. 
We  often  move  to  avoid  injury.  Motion  is  necessary  for 
speech  and  in  the  use  of  the  sense  organs.  How  are  all 
these  motions  produced? 

Experiments  with  the  Muscles  in  our  own  Bodies.  —  i .  Clasp  the 
front  of  the  right  upper  arm  ;  draw  up  the  forearm  strongly  and  as  far 
as  possible.  Note  the  changes  that  are  felt  in  the  biceps  muscle. 


Fig.  10.    The  Shortening  and  Thickening  of  the  Biceps  Muscle  in  raising  the  Forearm 

2.  Repeat  the  experiment,  and  with  the  thumb  and  finger  feel  the 
cord,  or  tendon,  at  the  lower  end  of  the  muscle,  just  within  the  angle  of 
the  elbow. 

16 


Muscles  and  Motion.  17 

3.  Span  the  muscle,  placing  the  tips  of  the  fingers  in  the  angle  of  the 
elbow,  and  the  tip  of  the  thumb  as  far  as  you  can  up  the  arm ;   again 
bend  the  arm.     What  change  in  the  muscle  does  this  show  ?     Any 
muscle  that  bends  a  Ijmb,  as  does  the  biceps,  is  called  a  flexor  muscle. 

4.  Clasp  the  back  of  the  upper  right  arm ;  forcibly  straighten  the 
arm.     The  muscle  lying  along  the  back  of  the  arm  is  the  triceps  muscle. 
It  is  called  an  extensor  muscle  because  it  extends,  or  straightens,  the  arm. 

5 .  Clasp  the  upper  side  of  the,  right  forearm  near  the  elbow  ;  clench 
the  right  hand  quickly  and  forcibly ;  repeat  rapidly. 

6.  Notice  the  mass  of  muscle  at  the  base  of  the  thumb ;   pinch  the 
forefinger  and  thumb  strongly  together.     What  changes  can  be  seen  and 
felt? 

7.  Place  the  hand  on  the  outside  of  the  shoulder ;  raise  the  arm  to 
the  horizontal  position  ;  repeat  with  a  weight  in  the  hand. 

8.  Stand  erect  with  the  heels  close  to  each  other,  but  not  quite 
touching ;   let  the  arms  hang  freely  by  the  sides ;   rise  on  tiptoes,  with- 
out moving  otherwise  ;  repeat  ten  times. 

9.  Place  the  tips  of  the  fingers  on  the  angles  of  the  lower  jaw ;   shut 
the  teeth  firmly,  and  note  the  bulging  of  the  masse ter  muscle. 

10.  Press  the  fingers  on  the  temples  ;  again  shut  the  jaws  firmly,  and 
feel  the  action  of  the  temporal  muscles. 

By  these  experiments  we  learn  that  when  a  muscle  works 
it  becomes  shorter,  thicker,  and  harder. 

The  Action  of  Muscle.  —  The  action  of  muscle  is  always 
a  "  pull."  The  muscle  shortens,  at  the  same  time  thicken- 
ing and  hardening.  It  must  be  kept  clearly  in  mind  that 
the  work  of  the  muscle  is  done  by  its  shortening  and  not 
by  either  the  hardening  or  thickening.  But  the  hardening 
and  thickening  are  often  more  noticeable  than  the  shorten- 
ing, and  by  means  of  them  we  may  locate  the  muscle  that 
is  producing  any  motion. 

Action  of  Frog's  Muscle.  —  The  action  of  muscle  may  be  seen  much 
more  clearly  in  a  frog's  calf  muscle,  as  shown  in  Fig.  1 1 .  When  the 
nerve  is  stimulated  at  "  A  "  a  nerve  impulse  runs  along  the  nerve  to  the 
muscle  and  makes  it  shorten  and  widen,  raising  the  weight  as  shown  in 
the  right  half  of  the  figure. 


i8 


Physiology. 


SHORTENED 


ELONGATED 

Fig.  1 1 .     Action  of  the  Calf  Muscle  of  the  Frog,  showing  the  Relations  of  the 
Sciatic  Nerve. 

Structure   of   Muscle.  —  Chipped   beef   shows   well   the 
structure  of  muscle.      The  white   network  is  connective 

tissue.     Its  work  is  to  hold 
Origin  the  parts  of  the  muscle  to- 

^Bundle  of  Muscle  Fibers     gether     and     tO     Support     the 

muscle  as  a  whole.  In  the 
meshes  of  the  white  network 
is  the  red  muscle  tissue.  The 
partitions  which  run  all 
Muscle  sheath  \  through  the  muscle  are  con- 

CROSS   SECTION        .  .  ,  , 

tmuous  with  the  muscle 
sheath,  and  both  are  con- 
tinuous with  the  tendons  at 
the  ends  of  the  muscle.  In 
fresh  muscle  the  sheath  and 
the  partitions  are  transpar- 
ent, and  are  not  very  easily 

noticed.     When  meat  is  cooked  or  salted  the  connective 

tissue  becomes  white  and  opaque. 


f  Muscle   Fibers 
eath  \ 


Tendon 


Insertion 
LONGITUDINAL   SECTION 


Fig.  12.    The  Structure  of  Muscle. 


Muscles  and  Motion. 


Fig.  13.  Two  Striated  Muscle 
Fibers  showing  the  termina- 
tions of  the  Nerves. 


Microscopic  Structure  of  Muscle.  —  If  a  tiny  shred  of 
muscle,  such  as  you  may  remove  from  the  teeth  with  a 
toothpick,  be  put  in  a  drop  of 
slightly  salted  water  and  exam- 
ined under  a  good  microscope,  the 
fibers  may  be  seen.  These  are 
small  thread-like  bodies,  with  cross 
markings,  from  which  they  are 
called  striated  or  striped  mttscle 
fibers.  From  the  fact  that  they 
are  under  the  control  of  the  will 
they  are  called  voluntary  muscle 
fibers.  Not  all  striated  muscle 
fibers  are  voluntary.  The  heart 
muscle  fibers  are  in  a  special  class,  being  striated  but 
involuntary.  The  muscles  connected  with  the  bones 
are  called  skeletal  muscles.  They  are  all  striated  and 
all  voluntary. 

Plain  Muscle  Fibers.  —  In  the  walls  of  the  arteries,  of 
the  gullet,  the  stomach,  the  in- 
testines, the  bladder,  and  else- 
where, there  are  muscle  fibers 
of  a  different  kind  from  those  of 
the  skeleton.  These  fibers  are 
spindle-shaped  cells,  as  shown  in 
Fig.  14,  with  a  nucleus  near  the 
center,  and  do  not  have  the  cross- 
markings.  Hence  they  are  called 
plain,  smooth,  or  un-striated  mus- 
cle fibers.  Owing  to  the  fact 
that  they  are  not  under  the  con- 
trol of  the  will  they  are  called  involuntary  muscle  fibers. 


— Nucleus 


Isolated  Fibers 


"    Fibers  Joined 


Fig.  14.    Plain  (unstriated)  Muscle 
Fibers. 


20 


Physiology. 


The  involuntary  muscle  fibers  are  usually  much  slower  in 
their  action  than  the  voluntary  fibers. 

Heart    Muscle    Fiber.  —  The 

fibers  which  make  up  heart 
muscle  are  different  in  appear- 
ance from  either  the  striated  or 
the  smooth  muscle  fibers.  They 
are  more  or  less  branched,  as 
shown  in  Fig.  15.  No  sheath 
has.  been  found  on  these  fibers. 

A  Muscle  Fiber  is  a  Cell. - 

It  is  easily  seen  that  each  plain 
muscle  fiber  is  a  single  cell,  hav- 
ing its  distinct  nucleus.  The 

Fig.  is.  Muscle  Fibers  from  the  Heart,   same  is  true  of  the  heart  muscle 

magnified,  showing  their  cross  striae,  fib  though     they    are    not    SO 

divisions,  and  junctions.  J 

The  nuclei  and  cell-junctions  are  shown  simple,       being       more       Or       leSS 
only  on  the  right  hand  side  of  the 

figure.  branched. 

Effect  of  Cooking  Muscle.  —  In  well-cooked  corned  beef 
the  connective  tissue  is  thoroughly  softened,  and  the  mus- 
cle fibers  are  easily  separated.  Thorough  cooking,  espe- 
cially stewing,  will  soften  the  connective  tissue,  and  may 
make  tender  meat  that,  cooked  otherwise,  would  be  very 
tough  on  account  of  the  large  amount  of  connective  tissue. 

Imitation  of  Structure  of  Muscle.  —  Take  a  number  of  pieces  of  red 
cord  to  represent  the  muscle  fibers.  Wrap  each  in  white  tissue  paper; 
this  represents  a  single  fiber  sheath.  Lay  a  number  of  these  side  by 
side,  and  wrap  them  all  in  a  common  sheath.  Let  the  tissue  paper  pro- 
ject beyond  the  ends  of  the  threads,  and  here  compress  it  into  a  com- 
pact cylinder ;  this  last  represents  the  tendon. 

Connective  Tissue  the  Skeleton  of  Muscle.  —  If  all  the 

muscle  fibers  were  removed  from-  a  muscle,  the  sheaths 


Muscles  and  Motion.  21 

and  partitions  would  remain,  and  show  the  form  of  the 
muscle  just  as  the  partitions  remain  in  a  squeezed  orange 
or  lemon.  The  connective  tissue  forms  a  framework  for 
all  the  soft  tissues  of  the  body,  and  if  their  working  cells 
were  removed,  the  connective  tissue  would  remain,  and 
show,  more  or  less  completely,  the  form  of  the  part.  Con- 
nective tissue  may  be  called,  therefore,  the  skeleton  of  the 
soft  tissues.  Muscle  consists,  then,  of  soft  transparent 
tubes,  filled  with  a  semi-fluid  muscle  substance.  By  scrap- 
ing the  surface  of  a  steak  the  muscle  substance  may  be 
obtained,  leaving  the  connective  tissue.  This  is  a  good 
way  to  get  the  nutritious  part  of  beef  for  an  invalid. 

Importance  of  Muscles.  —  The  muscles  make  up  nearly 
half  the  weight  of  the  body.  This  fact  of  itself  should 
lead  us  to  conclude  that  the  muscles  are  of  great  impor- 
tance. Muscles  are  used  in  nearly  every  action  of  the 
body,  not  only  in  locomotion,  but  in  respiration,  circulation, 
digestion,  speech,  etc.  It  is  very  necessary  that  at  the 
beginning  we  understand  their  action. 

Duration  of  Muscle  Shortening.  —  A  muscle  cannot  be 
kept  shortened  for  any  great  length  of  time.  If  one  holds 
the  arm  out  horizontally  as  long  as  he  can,  he  soon  feels 
fatigue,  later  pain,  and  he  is  likely  to  feel  a  soreness  in  the 
muscle  for  several  days  afterward.  The  law  of  muscle 
action  is  to  alternate  periods  of  rest  with  periods  of  action. 
In  many  exercises,  as  in  walking,  the  limbs  act  alternately, 
one  resting  or  recovering  while  the  other  works. 

Alternate  Action  of  Flexors  and  Extensors.  —  When  the 
biceps  muscle  shortens  and  bends  the  arm,  the  triceps 
lengthens  (see  Fig.  16).  When  the  triceps  shortens,  as  in 
straightening  the  arm,  the  biceps  lengthens.  If  the  biceps 
and  triceps  both  shorten  at  the  same  time,  and  with  equal 


22 


Physiology, 


Deltoid  


Serratus  Magnus.... 


Rectus  Femoris 


Tibialis  Anticus 


Pectoralis  Major 


Rectus  Abdominalis 


Extensors  of  the   Hand 
Flexors  of  the  Hand 


Sartorius 


Vastus  Externus 


Extensors  of  the  Toes 


Fig.  16.    Front  View  of  the  Superficial  Muscles 


Muscles  and  Motion. 


Extensors  of  the  Hand 


Triceps— 


Latissimus  Dorsi.... 


Gluteus  Maximus 


Vastus  Externus.... 


Ftexors  of  the  Foot 


Trapezius 


..-  Deltoid 


...  Flexors  of  the  Hand 


Biceps  Cruris 


.  Gastrocnemius 


Tendo  Achi 


Fig.  17-     Back  View  of  the  Superficial  Muscles. 


24  Physiology. 

force,  no  motion  will  be  produced.  Sometimes  this  is  done 
on  purpose,  as  when,  in  wrestling  "square-hold,"  one  holds 
the  arm  rigidly  bent  at  a  right  angle,  to  keep  his  opponent 
from  either  pushing  or  pulling  him.  In  the  body  are  many 
flexors  and  extensors  " paired  off";  they  act  alternately, 
like  the  biceps  and  triceps  in  the  arm. 

Symmetrical  Development  of  the  Muscles.  —  The  muscles 
of  the  two  sides  of  the  body  are  the  same  in  number  and 
arrangement.  At  birth  they  are  probably  about  equal  in 
size,  weight,  and  strength.  Most  persons  early  become 
right-handed,  and  the  greater  use  of  the  right  hand  and 
shoulder  makes  the  muscles  of  this  side  larger  and  heavier. 
The  muscles  pulling  on  the  bones  slightly  modify  them  in 
shape.  The  whole  body  may  become  noticeably  one-sided. 
Most  persons  step  harder  on  one  foot  than  on  the  other,  as 
shown  by  the  sound  of  the  footstep,  or  by  the  constant 
wearing  of  one  shoe  sole  or  heel  faster  than  the  other.  In 
many  persons  one  shoulder  is  carried  higher  than  the 
other. 

To  Overcome  One-sidedness.  —  Symmetrical  development 
should  be  carefully  sought,  and  any  tendency  to  a  one- 
sided development  should,  so  far  as  possible,  be  avoided. 
We  should  use  the  left  hand  more.  There  are  many  ad- 
vantages in  being  able  to  use  either  hand.  In  carving,  in 
shaving,  in  bandaging,  in  giving  medicine,  it  may  be  neces- 
sary to  use  the  left  hand  skillfully.  The  pianist  and  the 
harpist  use  the  two  hands  about  equally,  while  the  violinist 
puts  much  more  skill  into  his  left  hand.  Trainers  of 
athletes  often  begin  by  developing  the  left  side  of  the 
body  till  it  equals  the  right  in  size  and  strength. 

Muscles  the  Source  of  Strength.  — Our  strength  depends 
on  our  muscles.  It  is  a  fine  thing  to  have  strong,  well- 


Muscles  and  Motion.  25 

developed  muscles,  not  only  because  they  give  beauty  of 
form,  but  because  extra  strength  and  endurance  may  be 
needed  in  case  of  accident,  to  save  one's  own  life  or  that 
of  others.  In  a  case  of  fire  the  ability  to  climb,  to  go  up 
or  down  a  rope  "  hand  over  hand,"  may  be  all-important. 
Any  one's  life  may  depend  on  his  ability  to  run  far  and 
swiftly,  to  swim,  to  jump,  or  to  lift  a  heavy  weight 

The  Number  of  Muscles.  —  There  are  over  five  hundred 
muscles  in  the  human  body.  These  vary  in  size  from  less 
than  an  inch  in  length,  in  the  ear  and  in  the  larynx,  to  a 
foot  and  a  half  long  in  the  thigh. 

The  Arrangement  of  Muscles.  —  The  muscles  of  the  two 
sides  of  the  body  are  paired,  and  naturally  are  about  equal 
in  size  and  strength.  The  muscles  of  the  limbs  are  further 
paired  into  flexors,  which  bend,  and  the  extensors,  which 
straighten  the  limbs.  The  muscles  are  also  arranged  more 
or  less  in  layers.  There  is  generally  an  outer  layer  and  a 
more  deep-seated  layer. 

Forms  of  Muscles.  —  Muscles  are  of  various  shapes. 
The  prevailing  form  in  the  limbs  is  spindle-shaped,  or 
fusiform.  Some  muscles  are  flat,  some  have  their  fibers 
arranged  like  the  barbs  of  a  feather,  and  are  hence  called 
penniform.  Some  muscles  have  a  tendon  in  the  middle 
which  runs  through  a  loop,  as  in  the  case  of  the  muscle 
which  depresses  the  lower  jaw.  Muscles  which  close  open- 
ings are  circular,  and  are -called  sphincter  muscles. 

Peculiar  Muscles.  — The  diaphragm  is  a  sheet  of  muscle 
that  forms  a  partition  between  the  chest  and  the  abdomen. 
It  is  arched^  and  has  a  clear  tendinous  center.  The  ab- 
dominal muscles  form  a  wall  to  hold  the  organs  of  the 
abdominal  cavity.  These  muscles  also  aid  in  breathing, 
3— PHY 


26  Physiology. 

especially  in  f.orced  expiration,  as  after  violent  exercise  and 
in  coughing.  The  abdominal  wall  consists  of  several  layers 
of  muscle. 

Muscles  of  Expression.  —  The  facial  expression  is  due 
to  the  action  of  the  muscles  of  the  face,  which  in  turn  are 
under  control  of  the  cranial  nerves.  The  habitual  position 
becomes  somewhat  "  fixed,"  so  it  is  true  that  character  is 
often  shown  by  "the  looks."  Cultivation  of  happy  thoughts 
therefore  tends  to  make  one  better  looking. 

Muscles  and  Fat.  —  Fat  fills  in  space  between  muscles, 
and,  if  abundant,  forms  a  layer  over  the  muscles.  One 
notable  instance  is  the  hollow  triangular  space  between 
the  muscles  of  the  cheek.  If  there  is  very  little  fat,  a 
depression  is  seen,  forming  the  "  hollow  cheeks."  But  an 
abundance  of  fat  makes  a  corresponding  elevation. 

Convulsions.  —  These  spasmodic  actions  are  due  to  dis- 
ordered action  of  the  muscles,  and  to  a  disturbed  action 
of  the  nervous  system  that  controls  the  muscles.  Various 
disturbances,  such  as  indigestion,  may  by  reflex  action 
bring  on  convulsions. 

Summary.  —  i.  Motion  is  involved  in  nearly  every  action  of  the  body. 

2.  The  action  of  muscle  is  a  shortening,  accompanied  by  a  thicken- 
ing and  hardening. 

3.  Muscle  consists  of  fibers  with  a  connective  tissue  sheath  for  each 
fiber,  bundle  of  fibers,  and  for  the  muscle  as  a  whole. 

4.  The  skeletal  muscle  fibers  are  striated. 

5.  The  muscles  make  about  half  the  body's  weight. 

6.  Muscles  can  remain  shortened  only  a  little  while. 

7.  The  muscles  should  be  developed  symmetrically. 

8.  There  are  about  five  hundred  muscles  in  the  body. 

9.  The  muscles  of  the  two  sides  are  alike. 

10.    The  muscles  of  the  limbs  are  spindle-shaped. 

Questions.  —  i.  What  effect  is  produced  by  carrying  a  heavy  satchel 
for  a  long  distance  without  resting  ? 


Muscles  and  Motion.  27 

2.  Which  is  more  tiresome,  standing  still  or  walking?     Why? 

3.  When  the  boy,  who  thinks  he  can  strike  a  hard  blow,  says, 
"  Feel  my  muscle,"  does  he  usually  call  attention  to  the  muscle  used  in 
striking? 

4.  Why  are  the  sides  of  the  body  often  sore  after  walking  on  icy 
pavements  ? 


CHAPTER   IV. 
THE  MUSCLES  AND  THE  BONES. 

Skeletal  Muscles.  —  When  we  look  at  the  skinned  car- 
cass of  an  animal  in  the  market,  we  observe  that  the  mus- 
cles almost  completely  cover  the  bones.  Those  which  are 
attached  to  the  bones  are  called  skeletal  muscles.  They 
act  upon  them  as  levers,  making  the  motion  strong,  quick, 
and  accurate.  Without  bones  our  motions  would  be  like 
those  of  an  earthworm  or  slug,  slow  and  uncertain.  The 
muscles,  acting  through  the  bones,  can  lift  a  weight  that 
would  crush  the  muscles  if  laid  directly  upon  them,  while 
a  bone,  able  to  support  a  heavy  weight  without  being 
crushed,  has  no  power  in  itself.  The  muscles  have  active 
strength,  the  bones  have  passive  strength. 

Relation  of  the  Muscles  and  the  Bones.  —  Examine  Figs. 
10,  1 6,  and  17.  For  this  work  you  should  have  the  bones  of 
an  arm.  Locate  the  biceps  muscle  in  its  relations  to  these 
bones  as  shown  in  the  figures.  Feel  the  biceps  of  your 
arm.  Note  that  its  thickest  part  is  opposite  the  most 
slender  part  of  the  bone.  But  at  the  enlarged  end  of  the 
bone  the  muscle  has  narrowed  to  a  slender  tendon  which 
passes  over  the  joint  to  be  attached  to  the  next  bone,  thus 
giving  more  slenderness,  flexibility,  and  freedom  of  motion 
to  the  joint.  Most  of  the  skeletal  muscles  are  attached  to 
bones.  There  are  some  exceptions,  such  as  the  circular 
muscle  which  closes  the  mouth  when  the  lips  are  pursed  up. 

X-Rays  and  their  Use,  —  By  means  of  X-ray  apparatus 

28 


The  Muscles  and  the  Bones, 


29 


Fig    18.     X-Ray  Photograph  of  Hand  showing  Shot  carried  for  Twenty  Years. 
(From  Recreation,  by  permission  of  G.  O.  Shields.) 

the  physician  can  photograph  through  the  body  and  show 
the  location  of  the  bones.  This  process  is  useful  in  show- 
ing injuries  to  the  bones.  It  is  also  especially  useful  in 


30  Physiology. 

locating  a  bullet  or  other  solid  body  in  the  flesh,  which 
probing  of  ten,  fails  to  discover. 

Levers.  —  The  main  facts  to  be  learned  about  a  lever  are 
that  it  is  a  rigid  bar ;  the  point  about  which  the  lever  turns 
is  called  the  fulcrum ;  the  place  where  the  power  is  ap- 
plied is  called  the  power ;  and  the  part  to  be  moved  is 
called  the  weight.  In  the  body,  the  fulcrum  is  some  joint, 
the  power  is  the  place  where  the  muscle  is  attached,  and 
the  weight  is  the  part  to  be  moved. 

Kinds  of  Levers. — There  are  three  kinds  of  levers.  In 
the  first  class  the  fulcrum  is  between  the  power  and  the 
weight,  as  in  prying  over  a  block  with  a  crowbar.  In 
the  second  class  the  weight  is  between  the  power  and 
the  fulcrum,  as  in  a  wheelbarrow.  In  the  third  class  the 


(I)  Tapping  on  Floor.  (2)  Rising  on  Toe.  (3)   Lifting  Weight 

Fig.  19.    Three  Kinds  of  Levers  as  shown  by  the  Foot. 
P  —  Power.     W—  Weight.     F  —  Fulcrum. 

power  is  between  the  fulcrum  and  the  weight,  as  in  rais- 
ing the  forearm  (see  upper  part  of  Fig.  19).  We  may 
find  many  examples  of  levers  in  the  body  if  we  look  for 
them. 

Kinds  of  Levers  shown  by  the  Foot.  —  The   different 


Ball 


Articular  Extremity 


The  Muscles  and  the  Bones.  31 

classes  of  levers  may  be  illustrated  by  different  motions 

of  the   foot.      In   tapping   the   toes   on   the   floor  while 

the  heel  is  lifted,  or  in  pressing  down  the  ball  of   the 

foot  while  running  the  treadle  of 

a  sewing  machine,  we   have  an 

example  of  a  first-class  lever.     In 

raising  the  weight  of  the  body  on 

tiptoes,  or  as  the  foot  is  used  in 

taking  each  step,  the  foot  is  used 

as  a  lever  of   the  second  class. 

When  one  lifts  a  weight  with  the 

toes,  the  foot  is  used  as  a  lever 

of  the  third  class.    (See  Fig.  19.) 

Advantages  of  Levers  in  the  Body.  -  Medullary  Cavity 

If  the  arm  consisted  merely  of  the  biceps 
muscle,  suspended  from  the  shoulder,  it 
is  evident  that  its  only  action  would  be 
a  straight  pull.  Suppose  the  biceps, 
thus  hanging  alone  from  the  shoulder, 
had  a  hook  at  its  lower  end,  it  could, 
when  it  shortened,  lift  a  weight  just  as 
far  as  it  shortened,  and  no  farther.  It 
could  not  swing  the  weight  outward,  or 
push  it  upward.  But  from  the  way  in 
which  the  biceps  is  attached  to  the  fore-, 
arm  (see  Fig.  10),  when  the  muscle 
shortens  an  inch  it  may  move  the  hand  Fig.  20. 
a  foot.  Of  course  the  hand  moves  much 
faster,  and  we  have  a  great  gain  in  speed  by  reason  of  this  lever  arrange- 
ment. But  we  cannot  lift  so  heavy  a  weight  at  this  faster  rate,  as  we 
could  at  the  elbow. 

Study  of  One  of  the  Long  Bones.  —  For  this,  take,  preferably,  a  femur 
or  a  humerus.     Let  us  suppose  we  have  a  femur. 

i.   Observe  its  shape,  —  cylindrical,  somewhat  curved,  enlarged  at 
the  ends. 


Hard  Bone 


Spongy  Bone 
Articular  Extremity 


Longitudinal   Section    of 
Femur. 


Physiology. 


2.  The  ends  have  smooth  places,  where  they  fitted  other  bones. 

3.  Along  the  sides,  especially  near  the  ends,  are  ridges  and  projec- 
tions, where  the  muscles  were  attached. 

4.  There  are  small  holes  in  the  bone,  where  blood  tubes  passed  in 

and  out. 

5 .  Saw  a  femur  in  two,  lengthwise,  and  make 
a  drawing  showing :  — 

(a)  The  central  marrow  cavity. 
(£)  The  spongy  extremities,  noting  especially 
the  directions  of  the  bony  plates  and  fibers. 

6.  Observe  the  width  of  the  lower  end  of 
the  femur,  where  it  rests  on  the  tibia.     Sup- 
pose these  two  bones  were  as  narrow  at  their 
ends,  where  they  meet  to  form  the  knee  joint, 
as  they  are  at  their  centers,  what  kind  of  a  joint 
would  they  make  ?      Illustrate  by  piling  up  a 
number  of  spools  on  end ;  the  column  is  more 
lightened  than  it  is  weakened  by  the  hollow- 
ing out  of  the  sides  of  each  spool.     And  the 
central  hollow  of  the  spool  does  not  greatly 
weaken  it. 

Joints.  — The  ends  of  the  bones,  where  they 
fit  together  in  the  joints,  are  covered  with  a 
layer  of  smooth,  elastic,  whitish  or  transparent 
cartilage.  The  motion  in  the  joints  is  made 
still  more  easy  by  the  synovia,  resembling  white 
of  egg.  The  ends  of  the  bones  are  held  to- 
gether by  tough  bands  and  cords  of  ligament, 
a  form  of  connective  tissue  very  much  like  ten- 
don. Bones  are  closely  covered  by  a  tough 
coat  of  connective  tissue  called  the  periosteum. 

All  these  structures  can  easily  be  found  by 
dissecting  a  sheep  shank  gotten  from  the 
butcher,  or  in  the  hind  leg  of  a  rabbit. 


Fig.  2 1 .   Action  of  the  Mus- 
cles in  Standing. 


.  Standing.  —  Although  we  are  not  ordinarily  conscious 
of  the  fact,  when  we  are  standing  still  we  are  using  many 
muscles.  The  accompanying  figure  illustrates  how  some 
of  the  muscles  act  in  keeping  the  body  upright.  Our 


The  Muscles  and  the  Bones.  33 

weight,  or,  we  would  better  say,  the  force  of  gravity,  is 
continually  trying  to  pull  us  down  to  the  ground.  The 
joints  are  all  freely  movable,  and  hence  as  soon  as  the 
muscles  cease  to  act  properly,  in  balancing  against  each 
other,  we  lose  our  balance,  and  fall  if  we  do  not  quickly 
regain  it. 

Walking.  —  In  walking,  we  lean  forward,  and  if  we  take 
no  further  action  we  fall.  But  we  keep  one  foot  on  the 
ground,  pushing  the  body  forward,  while  the  other  leg  is 
bent  and  carried  forward  to  save  us  from  the  fall.  We 
catch  the  body  on  this  foot,  and  repeat  the  action.  To 
show  how  we  are  really  repeatedly  falling  and  catching 
ourselves,  recall  how  likely  one  is  to  fall  if  some  obstacle 
is  placed  in  the  way  of  the  foot  as  it  moves  forward  to 
catch  the  weight  of  the  body. 

Running.  —  In  running,  the  action  is  more  vigorous. 
The  force  exerted  by  the  rear  leg  is  now  greater.  It  gives 
such  a  push  as  to  make  the  body  clear  the  ground,  whereas 
in  walking,  the  rear  foot  is  not  lifted  till  the  front  foot 
touches  the  ground.  But  in  running  there  is  a  time  when 
both  feet  are  off  the  ground. 

Locomotion  by  Reaction.  —  Take  two  broomsticks  and  place  them 
crosswise  under  the  ends  of  a  board.  Run  along  the  board.  This 
shows  that  the  direct  effort  in  running  is  to  push  one's  support  from 
under  him.  Our  effort  in  moving  forward  is  to  push  the  earth  out  from 
under  us,  and  it  is  by  reaction  that  we  go  forward.  It  is  the  same 
problem  with  the  fish  swimming  forward  by  striking  backward  and 
sideways  against  the  water,  and  with  the  bird  beating  downward  and 
backward  upon  the  air. 

Bones  combine  Lightness  and  Strength.  —  The  muscles, 
then,  make  use  of  the  bones  as  levers.  We  carry  these 
levers  with  us  all  the  time.  Hence  the  desirability  of  hav- 
ing them  light  as  well  as  strong.  A  hollow  pillar  or  hoi- 


34  Physiology. 

low  tube  has  greater  strength  than  the  same  amount  of 
material  in  the  form  of  a  solid  cylinder.  The  long  bones 
of  the  limbs  are  hollow,  and  near  their  ends,  where  we 
have  found  that  they  need  to  be  enlarged,  we  find  a 
spongy  structure,  where  lightness  and  strength  are  secured 
by  the  interlacing  fibers  and  plates  of  bony  material. 

Muscles   always   Stretched.  —  The  muscles   are   always 
slightly  stretched,  as  shown  by  the  fact  that  when  a  cut 

is  made  into  a  muscle  the 
wound  gapes  open;  the  ten- 
sion of  the  muscle  is  further 
shown  by  the  fact  that  when 
a  bone  is  broken,  as  in  the 
upper  arm  or  thigh,  the  ends 
of  the  bones  may  slip  by  each 
other,  and  the  limb  has  to  be 
strongly  stretched  to  bring  the 
ends  back  together.  Muscles 
act  better  when  slightly 
stretched,  and  probably  need  a 
slight  resistant  action  of  the 
opposing  muscle. 

What  makes  the  Muscles  act 

Fig.  22.    Fracture  of  the  Humerus. 

in  Harmony  ?  —  Have  you  ever 

seen  two  persons,'  one  using  the  right  hand  and  the  other 
the  left,  try  to  sew,  one  holding  the  cloth,  the  other  using 
the  needle?  Would  they  get  along  well?  Suppose  one 
were  to  hold  the  needle,  and  the  other  were  to  try  to  thread 
it,  each  using  one  hand.  Why  is  it  that  the  right  and  left 
hands  of  two  persons  cannot  work  so  well  together  as  the 
right  and  left  hands  of  one  person  ?  What  connection  is 
there  between  the  two,  that  one  knows  just  what  the  other 


The  Muscles  and  the  Bones.  35 

is  doing  and  when  it  does  it  ?  Why  can  two  individuals 
never,  with  any  amount  of  practice,  work  so  in  unity  as  the 
parts  of  the  individual  ? 

Let  us  seek  the  answer  to  these  questions  in  the  follow- 
ing lessons. J 

Reading.  — "  How  to  Get  Strong  and  How  to  Stay  So,"  Blaikie, 
"  Sound  Bodies  for  Our  Boys  and  Girls,1'  Blaikie. 

Summary.  —  i .  In  the  limbs  the  muscles  are  spindle-shaped  and  have 
their  greatest  diameter  opposite  the  central,  or  narrower,  portions  of  the 
bones,  concealing  the  fact  that  the  bones  are  largest  at  the  ends,  as  is 
so  evident  in  the  skeleton. 

2.  The  bones  serve  as  levers  by  which  the  muscles  exert  their  force. 

3.  The  bones  of  the  limbs  are  hollow  cylinders  combining  lightness 
and  strength. 

4.  The  joints  have  a  smooth  motion  due  to  the  cartilage  and  synovia. 

5.  Locomotion  is  brought  about  by  reaction. 

Questions.  —  i.    Find  other  examples  of  levers  in  the  body. 

2.  Find  examples  of  the  three  kinds  of  levers,  not  in  the  body,  which 
we  use  often. 

3.  Why  is  it  easier  to  sit  with  one  leg  crossed  over  the  other  ? 

4.  How  may  the  arms  be  used  to  illustrate  the  three  kinds  of  levers  ? 

5.  Analyze  and  explain  jumping,  hopping,  etc. 


CHAPTER   V. 

THE    GENERAL  FUNCTIONS    OF  THE  NERVOUS  SYSTEM. 
—  SENSATION  AND  MOTION. 

What  makes  Muscles  Shorten?  —  We  have  seen  that  the 
muscles  have  the  power  of  shortening ;  that  in  shortening 
they  act  on  the  bones  as  levers  to  produce  our  varied  mo- 
tions. What  makes  the  muscles  shorten  ? 

Voluntary  and  Involuntary  Motions.  —  Some  motions  we 
will  to  make.  We  will  to  sit,  to  stand,  to  walk,  to  run,  or 
to  stretch  out  the  hand.  Such  motions,  originating  in  a 
brain  activity,  are  called  voluntary.  Other  motions  are 
involuntary.  The  will  does  not  control  the  heart-beat. 
Most  persons  cannot  keep  from  winking  when  a  quick 
motion  is  made  toward  the  face,  even  if  they  know  they 
will  not  be  hit.  But  all  of  these  motions,  both  voluntary 
and  involuntary,  depend  upon  the  nervous  system. 

The  Cerebro-spinal  Nervous  System.  —  This  consists  of 
the  brain,  the  spinal  cord,  and  the  spinal  nerves. 

The  Brain.  —  There  are  two  main  parts  of  the  brain,  the 
cerebrum,  which  fills  all  the  upper  part  of  the  cranium, 
and  the  cerebellum,  very  much  smaller,  in  the  lower  back 
part  of  the  cranium.  The  cerebrum  is  divided  into  right 
and  left  hemispheres  by  a  lengthwise  groove.  The  sur- 
face of  the  cerebrum  is  covered  with  ridges  called  convo- 
lutions. The  outside  of  the  brain  is  of  gray  matter, 
consisting  of  cells,  while  the  inside  is  white,  consisting  of 
nerve  fibers. 

36 


Nervous  System. 


37 


Fig.  23.    The  Cerebro-spinal  Nervous  System. 

Two  Functions  of  the  Brain.  —  Only  two  functions  of  the 
brain  are  to  be  noticed  now.  One  is  sensation,  the  other 
motion,  or  rather  the  control  of  motion.  Nerve  currents 
that  come  to  the  brain,  produce  all  our  sensations.  Sen- 


38  Physiology. 

sation  is  in  the  gray  matter  on  the  outside  of  the  brain. 
When  we  wish  to  move  any  part  of  the  body,  the  first 
thing  is  to  will  to  do  it.  This  action  is  also  in  the  gray 
matter  on  the  outside  of  the  brain,  but  in  different  parts 
from  those  which  have  sensation.  The  act  of  willing  to  do 
anything  sends  nerve  currents,  or  impulses,  along  nerve 
fibers  to  the  part  that  is  to  be  set  to  work.  The  white 
fibers  of  the  inside  of  the  brain  connect  the  cells  of  the 
gray  matter  with  the  various  parts  of  the  body  through  the 
base  of  the  brain,  the  spinal  cord,  and  the  spinal  nerves. 

The  Spinal  Cord.  —  The  spinal  cord  is  a  cylindrical  body 
extending  from  the  brain  along  the  cavity  of  the  spinal 
column.  Its  diameter  is  not  uniform  throughout.  Between 
the  shoulders  is  an  enlargement  called  the  cervical  enlarge- 
ment, where  the  large  nerves  are  given  off  to  the  arms. 
In  the  region  of  the  loins  is  the  lumbar  enlargement,  where 
the  nerves  are  given  off  to  supply  the  legs.  The  outside 
of  the  cord  is  white,  but  the  central  portion  consists  of 
gray  matter.  The  white  portion  is  made  up  of  fibers,  but 
the  gray  matter  consists  of  nerve  cells  as  well. 

The  Spinal  Nerves.  —  These  are  given  off  in  pairs  from 
the  sides  of  the  spinal  cord.  They  pass  out  through  notches 
between  the  successive  vertebras,  so  there  is  no  danger  of 
their  being  crushed,  or  even  pinched,  when  the  backbone 
bends.  In  the  regions  of  the  shoulders  and  loins  the 
spinal  nerves  are  large,  as  they  supply  the  large  muscles 
of  the  limbs ;  but  in  the  middle  of  the  back,  where  only 
the  muscles  of  the  body  wall  are  supplied,  the  nerves  are 
small.  We  have  thirty-one  pairs  of  spinal  nerves. 

The  Roots  of  the  Spinal  Nerves.  —  Each  spinal  nerve 
arises  by  two  roots,  one  nearer  the  back,  called  the  dorsal 


Nervous  System.  39 

root,  the  other  nearer  the  ventral  surface,  the  ventral  root 
These  two  roots  soon  unite  to  form  one  spinal  nerve. 

Structure  of  Nerves.  —  If  we  trace  a  nerve  outward,  we 
find  that  it  is  continually  subdividing.  This  division  con- 
tinues until  the  branches  are  too  small  to  be  seen  by  the 
naked  eye.  Microscopic  examination  shows  that  a  nerve 
is  made  up  of  a  great  number  of  fibers  bound  together  in 
a  common  sheath  of  connective  tissue,  as  is  the  case  with 
muscle.  When  the  nerve  divides,  there  is  ordinarily  no 
true  branching  or  forking,  but  certain  of  the  fibers  simply 
separate  from  the  rest,  as  in  the  separation  of  the  fibers  in 
floss  silk. 

Nerve  Fiber  Sheath 


Axis  Cylinder 


Medullary  Sheath 
Fig.  24.    Structure  of  a  Nerve  Fiber. 

Structure  of  a  Nerve  Fiber.  —  A  single  nerve  fiber  is  too 
small  to  be  seen  by  the  naked  eye,  being  only  about  one 
two-thousandth  of  an  inch  in  diameter.  It  consists  of  the 
following  parts  :  — 

1.  The  axis  cylinder,  a  central  strand,  or  core,  of  semi- 
transparent,  gray  material. 

2.  The  medullary  sheath  is  a  layer  of  white,  oily  ma- 
terial around  the  axis  cylinder. 

3.  The  nerve  fiber  sheath  is  a  thin,  transparent  outer 
sheath  of  connective  tissue. 

Function  of  Nerve  Fibers.  —  The  only  function  of  the 
nerve  fiber  is  to  convey  nerve  impulses.  The  nerve  im- 
pulse passes  along  the  axis  cylinder  as  an  electric  current 
passes  along  an  insulated  wire. 


4O  Physiology. 

Afferent  and  Efferent  Nerve  Fibers.  —  Nerve  fibers  that 
carry  impulses  toward  the  spinal  cord  or  brain  are  called 
afferent  nerve  fibers.  Fibers  that  convey  impulses  from 
the  brain  or  spinal  cord  are  efferent  nerve  fibers. 

Cross-section  of  the  Spinal  Cord.  —  If  a  thin  slice  of 
the  spinal  cord  be  made  as  shown  in  Fig.  25,  it  will  be 
seen  that  the  central  part  is  darker  in  color  than  the  outer 
part.  The  central  part  is  known  as  the  gray  matter,  in 
distinction  from  the  rest,  which  is  called  the  white  matter. 

Dorsal  Septum 


Dorsal  or  Sensor 
Root 


Ventral  Fissure 
Ventral  or  Motor  Root 

Fig.  25.    Cross-section  of  Spinal  Cord. 

The  white  matter  of  the  nervous  system  is  made  up  of 
nerve  fibers,  whose  structure  and  use  we  have  just  con- 
sidered. "  But  the  gray  matter  has  a  different  structure  and 
a  different  function.  Instead  of  being  made  up  mainly  of 
fibers,  it  is  composed  of  cells,  one  of  the  forms  of  which  is 
represented  in  Fig.  26.  Some  of  the  branches  of  these 
cells  are  continued,  and  become  the  axis  cylinders  of 
nerves,  and  it  is  believed  that  every  nerve  fiber  begins  as 
a  branch  of  some  nerve  cell. 


Nervous  System. 


Functions  of  the  Spinal  Cord.  —  The  spinal  cord  has  two 
main  functions :  — 

i.    Its  conducting  power,  by  means  of  the  white  fibers 
which  make  up  the  outer  part  of  the  cord.     These  fibers 

connect  the  gray  matter  of 
the  brain  with  all  parts  of  the 
body,  and  carry  messages  to 
and  from  the  brain. 

2.    The  gray  matter  is  the 
center  of  the  reflex  actions  of 


Branched  Processes 


Fig.  26.    A   Large   Nerve   Cell   from   the    4-V.p 
Gray  Matter  of  the  Spinal  Cord. 


the  cord. 

Ganglions.  —  Masses  of 
nerve  cells  make  up  nerve 
centers,  or  ganglions,  such 
as  are  on  the  dorsal  roots  of 
spinal  nerves.  These 
also  would  show  under  the 
microscope  that  their  chief  constituent  is  a  collection  of  nerve 
cells  which  give  off  one  or  more  branches.  The  gray  matter 
of  the  spinal  cord  is  a  collection  of  ganglions. 

Reflex  Action  in  a  Sleeping  Child.  —  If  the  sole  of  the  foot  of  a  sleep- 
ing child  is  gently  tickled,  the  foot  will  be  drawn  up.  The  child  has  no 
sensation.  The  brain  has  nothing  to  do  with  it.  It  is  purely  reflex 
action.  A  nerve  impulse  has  gone  to  the  spinal  cord,  and  another 
impulse  has  been  sent  out  to  make  the  needed  movement.  But  some- 
times the  child  may  be  half  awake  and  the  foot  might  be  drawn  up  by 
voluntary  action.  Let  us  take  another  case,  with  which  nearly  every 
one  is  familiar,  to  show  that  the  brain  has  nothing  to  do  with  reflex 
action. 

A  Hen  with  its  Head  cut  off.  —  Nearly  everybody  knows  that  after  a 
hen's  head  is  cut  off,  it  "flops"  around  for  some  time,  and  that  fre- 
quently when  one  takes  hold  of  its  feet  to  pick  it  up,  it  begins  to  struggle. 
Now  this  also  is  reflex  action  of  the  spinal  cord.  And  there  can  be  no 
doubt  that  the  brain  has  nothing  whatever  to  do  with  it. 
4 — PHY 


42  Physiology. 

The  Gray  Matter  of  the  Cord  the  Center  of  Reflex 
Action.  —  In  reflex  action  the  current  runs  up  the  nerve 
to  the  spinal  cord.  The  gray  matter  of  the  central  part  of 


Afferent  Dorsal   Root 

Sensor  Fiber 


Motor  Fiber 

Efferent  v 

Ventral   Root 

Fig.  27.     Diagram  of  Reflex  Action  of  the  Spinal  Cord. 
(After  Landois  and  Stirling.) 

the  cord  receives  the  message,  and  sends  back  a  nerve 
impulse  to  the  muscles,  to  make  them  shorten  and  pull  the 
foot  away  from  the  source  of  irritation. 

The  Parts  Essential  to  Reflex  Action  of  the  Spinal 
Cord:  —  I.  A' sensitive  surface  (the  skin,  for  instance). 
2.  Afferent  nerve  fibers.  3.  A  nerve  cell,  or  cells,  in 
the  center  of  the  spinal  cord.  4.  Efferent  nerve  fibers. 
5.  Working  organ,  as  muscle  or  gland. 

Steps  in  Reflex  Action.  —  In  the  above  examples  the 
steps  in  order  are :  — 

i.  Stimulation  of  the  nerve  endings  in  the  skin  of  the 
foot.  2.  Passage  of  nerve  impulses  up  the  afferent  fibers 
to  the  spinal  cord.  3.  Reception  of  the  impulse  by  cells 
of  the  gray  matter  in  the  cord.  4.  Sending  back  nerve 
impulses.  5.  Along  efferent  fibers  to  6.  Muscles  which 
shorten  so  as  to  move  the  foot. 


Nervous  System. 


43 


Importance  of  Reflex  Action.  —  It  is  important  that  we 
understand  the  nature  of  reflex  action,  for  very  many  of 
the  processes  of  the  body  are  regulated  by  it.  Not  only 
such  motions  as  winking  when  anything  comes  quickly 

Nerve  Cells  Connected  by  Interlacing  Nerve  Network. 


Afferent  Nerve  Fiber 


Sensory 

Epithelium 

(Skin) 


Efferent  Nerve  Fiber 


Muscle 


Fig.  28.    Parts  used  in  Reflex  Action. 


toward  the  eye,  dodging,  jumping  when  suddenly  touched 
by  anything  hot  or  when  pricked  by  a  pin,  but  also  the 
regulation  of  circulation,  respiration,  and  digestion,  are 
brought  about  through  reflex  action. 

Destination  of  Nerve  Fibers.  —  The  sciatic  nerve  (the 
large  nerve  of  the  thigh,  see  Fig.  23)  is  composed  of  many 
fibers.  If  this  nerve  is  traced  outward,  it  is  found  to  be 
continually  subdividing  and  sending  smaller  branches  to 
the  muscles,  and  finally  in  the  muscles  one  fine  nerve  fiber 
goes  to  each  muscle  fiber.  (See  Fig.  13.)  Many  fibers  go 
on  past  the  muscles  to  the  skin.  We  can  feel  in  any  part 
of  the  skin,  and  we  can  tell  just  where  we  are  touched. 


44  Physiology. 

These  fibers  from  the  skin  carry  nerve  impulses  inward, 
as  those  going  to  the  muscles  carry  impulses  outward. 

Nerve  Roots  and  their  Functions.  —  Observations  made 
on  animals,  and  accidents  in  the  case  of  man,  show  that 
all  the  fibers  of  the  nerves  that  carry  currents  to  the  mus- 
cles pass  out  from  the  spinal  cord  into  the  ventral  root, 
and  that  all  the  fibers  that  carry  currents  inward  enter  the 
spinal  cord  through  the  dorsal  root.  Hence,  the  dorsal 
root  is  often  called  the  afferent  root,  and  the  ventral  the 
efferent  root.  Since  ingoing  impulses  produce  sensation, 
the  dorsal  root  is  called  the  sensory  root,  while  the  ventral 
root,  carrying  currents  outward  to  produce  motion,  is  called 
the  motor  root. 

Effect  of  Stimulating  a  Spinal  Nerve.  —  Experiments 
have  shown  that  if,  in  an  uninjured  animal,  a  nerve,  or 
more  properly  a  nerve  trunk  —  as  the  sciatic  nerve  —  be 
stimulated,  for  instance,  by  an  electric  shock,  two  effects 
are  produced :  first,  motion  in  the  parts  whose  muscles  are 
supplied  by  the  nerve ;  second,  sensation,  which  is  referred 
to  the  parts  of  the  skin  supplied  by  the  branches  of  the 
nerve.  This  double  effect  is  because  both  sets  of  fibers  in 
the  nerve  have  been  stimulated,  one  set  carrying  currents 
inward,  the  other  outward. 

Cramp.  —  Cramp  is  a  spasmodic  shortening  of  the  mus- 
cles, attended  with  pain. 

Tetanus.  —  Tetanus  (or  locked  jaw)  is  a  spasmodic  and 
continuous  shortening  of  the  muscles,  causing  rigidity  of 
the  parts  they  supply.  It  is  due  to  the  disordered  and 
excessive  stimulation  of  the  muscles  through  the  nerves. 

Crossing  of  the  Fibers  from  the  Brain  to  the  Spinal 
Cord.  — •  Both  the  brain  and  the  spinal  cord  consist  of  two 
lateral  halves  connected  by  cross  fibers.  Each  half  of  the 


Nervous  System.  45 

bfain  is  connected  with  the  opposite  half  of  the  body. 
This  is  accomplished  by  the  crossing  of  the  fibers.  The 
fibers  that  carry  nerve  impulses  outward  cross  as  they 
leave  the  brain,  at  the  very  beginning  of  the  spinal  cord, 
in  the  part  known  as  the  spinal  bulb.  The  sensations 
arising  from  .touching  anything  with  the  right  hand,  there- 
fore, are  in  the  left  half  of  the  brain,  and  the  right  half  of 
the  brain  controls  the  left  hand. 

Nervous  System  compared  to  a  Telegraph  System. — 
It  is  convenient  to  compare  the  nervous  system  to  a  tele- 
graph system.  Nerve  impulses  pass  along  the  nerve  fibers 
as  electric  currents  travel  along  the  wires.  The  ganglions, 
which  receive  and  send  impulses,  are  similar  to  the  offices 
which  receive  and  send  out  electric  currents.  But  there  is 
one  important  difference :  in  telegraphing,  the  same  wire 
is  used,  both  for  sending  and  receiving  messages ;  while 
in  the  nervous  system  there  are  two  sets  of  fibers,  one  for 
incoming  impulses  and  another  for  outgoing  impulses. 

Harmony  in  Muscle  Action.  —  In  throwing  a  stone  a 
number  of  muscles  are  used.  Each  muscle  shortens  under 
the  influence  of  a  nerve  impulse  started  by  the  brain  and 
brought  by  a  motor  nerve.  If  any  muscle  shortens  too 
soon,  or  a  little  too  strongly,  the  stone  goes  to  one  side. 
In  a  tune  on  a  piano  we  know  that  the  right  keys  must  be 
struck  at  the  right  time,  and  with  the  proper  force.  What 
the  player  is  to  the  instrument,  the  brain  is  to  the  body. 

Temporary  Loss  of  Muscular  Power.  —  It  may  have  hap- 
pened that  after  sitting  long  in  one  position  you  attempted  to 
stand,  but  could  not.  One  leg  failed  to  act  at  the  bidding 
of  your  will.  When  the  foot  is  "  asleep  "  we  get  little  sen- 
sation from  it ;  we  hardly  know  whether  it  is  touching  the 
floor.  Pressing  on  it  with  the  other  foot  causes  no  pain. 


46  Physiology. 

The  brain  starts  the  nerve  currents,  and  they  run  along 
the  nerve  as  far  as  the  compressed  part ;  here  they  stop. 
On  account  of  external  pressure  the  nerve  has  temporarily 
lost  its  power  of  conducting  nerve  currents.  They  cannot 
reach  the  muscles  of  the  leg  below.  Hence  the  muscles 
do  not  shorten,  and  we  do  not  rise,  no  matter  how  strongly 
we  will  to  do  so. 

Dependence  of  Nerves  and  Muscles.  —  But  what  beside 
the  nerve  has  been  compressed  ?  What  process  in  the 
limb  has  been  interfered  with  by  the  pressure  due  to  the 
position  in  which  one  has  been  sitting  or  lying  ?  What  is 
the  temperature  of  the  benumbed  limb  ? 

On  what  are  the  nerves  and  muscles  so  dependent  for 
keeping  up  their  activity  ? 

Summary.  —  i .  Motions  are  voluntary  or  involuntary,  but  all  are 
under  control  of  the  nervous  system. 

2.  The  cerebro-spinal  nervous  system  consists  of  the  brain,  the 
spinal  cord,  and  the  spinal  nerves. 

3.  Each  spinal  nerve  has  two  roots  :  the  dorsal,  which  is  afferent 
and  sensory ;  the  ventral,  which  is  efferent  and  motor. 

4.  A  ganglion  is  a  nerve  center  largely  composed  of  nerve  cells. 

5.  Nerves  are  made  up  of  nerve  fibers. 

6.  A  nerve  fiber  consists  of  the  central  core  (or  axis  cylinder), 
which  conducts  the  nerve  impulse,  the  medullary  sheath,  and,  outside, 
the  nerve-fiber  sheath. 

7.  The  spinal  cord  has  in  its  outer  part  white  nerve  fibers ;  in  its 
center,  gray  nerve  cells. 

8.  These  cells  are  branched,  and  at  least  one  branch  becomes  the 
axis  cylinder  -of  a  nerve  fiber. 

9.  The  gray  matter  of  the  cord  is  the  center  of  the  reflex  action. 
TO.    The  nerve  fibers  from  each  half  of  the  brain  connect  with  the 

opposite  half  of  the  body. 

11.    The  nervous  system  is  comparable  to  a  telegraph  system. 
Questions.  —  I.    Name  as  many  involuntary  motions  as  you  know. 

2.  What  other  cases  of  reflex  action  do  you  know  ? 

3.  Why  is  a  man  partially  paralyzed  when  he  has  broken  his  back  ? 


CHAPTER  VI. 
CIRCULATION  OF  THE  BLOOD. 

The  Blood  and  its  Work.  —  There  is  no  bleeding  when 
we  trim  the  nails  or  cut  the  hair,  and  the  outer  skin  has 
no  blood  in  it.  But  the  inner  skin,  and  almost  every  tissue 
within  it,  if  pierced  even  by  the  finest  needle,  yields  blood. 
We  know  that  loss  of  blood  causes  weakness,  and  may 
soon  cause  death. 

What  kind  of  a  substance  is  blood  ?  Why  is  it  so 
essential  to  life?  How  does  it  do  its  work? 

The  Rate  of  the  Heart  Beat  —  The  heart  beats  about 
seventy-two  times  a  minute.  In  children  it  beats  faster. 
The  rate  is  increased  by  exercise,  by  heat,  by  food,  and  by 
mental  excitement. 

The  Heart  Beat  and  the  Pulse.  —  I.  The  heart  beat  may  be  felt  at  the 
left  of  the  breastbone. 

2.  The  pulse  may  be  felt  at  the  wrist,  in  the  neck  beside  the  wind- 
pipe, and  in  various  parts  of  the  body.     Perhaps  the  most  convenient 
place  to  study  it  is  at  the -temple.     Lay  the  forefinger  lightly  along  the 
cheek  just  in  front  of  the  ear.     Count  the  pulsations  for  a  minute. 

3.  Let  one  or  two  pupils  step  to  the  blackboard  and  put  down  the 
number  of  pulsations  of  each  pupil,  and  divide  by  the  number  thus 
reporting,  to  get  the  average. 

4.  Let  all  count  the  pulse  while  sitting.     Get  the  average  of  the 
class. 

5.  Find  the  pulse  while  sitting ;  rise  quickly,  and  immediately  begin 
to  count  the  pulse.     Compare  with  the  pulse  as  taken  while  sitting. 

6.  Compare  the  pulse  before  and  after  meals. 

47 


48  Physiology. 

The  Shape  of  the  Heart.  —  The  heart  is  cone-shaped. 
But  the  point  or  apex  is  down,  and  the  big  end,  or  base, 
is  up,  so  when  we  speak  of  the  base  of  the  heart  we  mean 
the  upper  part,  not  the  lower. 

The  Position  of  the  Heart.  —  The  base  of  the  heart  is 
in  the  center  of  the  chest,  just  back  of  the  breastbone, 
but  the  apex  points  downward  and  to  the  left  (see  Figs. 
32  and  53). 


To  Head  and  Arms 
Pre-caval  Veinj 

Right  Auricle 


Aorta 


Left  Ventricle 


•Apex 
Fig.  29.    The  Heart,  from  the  front. 

The  Size  of  the  Heart  —  A  person's  heart  is  about  the 
size  of  his  clenched  hand. 

The  Covering  of  the  Heart.  — The  heart  is  inclosed  in  a 
loose-fitting  bag,  the  pericardium.  Within  the  pericardium 
and  around  the  heart  is  a  small  quantity  of  liquid,  called 
the  pericardia  I  fluid. 

The  External  Features  of  the  Heart.  —  The  larger  part 
of  the  heart  is  made  up  of  ventricles,  the  auricles  being 
two  ear-like  flaps  at  the  base,  one  on  each  side.  There 
is  a  deep  notch  between  the  auricles  and  the  ventricles. 


Circulation  of  the  Blood. 


49 


The  line  of  division  between  the  two  ventricles  is  marked 
by  a  groove,  which  runs  obliquely  along  the  front  surface. 
In  this  groove  are  blood  tubes  and  usually  some  fat.  (See 
Figs.  29  and  30.) 

The  Internal  Structure  of  the  Heart.  —  The  two  halves 
of  the  heart  are  completely  separated  from  one  another  by 
a  partition.  Each  half  has  valves  which,  part  of  the  time, 
separate  the  cavity  of  each  auricle  (at  the  base)  from  the 
cavity  of  the  ventricle  (at  the  apex). 


Aorta 
Left  Pulmonary  Artery 

Left  Pulmonary  Veins 
Left  Auricle 


Pre  caval  Vein 

Right  Pulmonary  Artery 

Right  Pulmonary  Veins 


Post-caval  Vein 


Right  Auricle 


Fig.  30.    The  Heart,  from  behind. 

The  Valves  of  the  Heart.  —  Between  the  auricles  and  the 
ventricles  are  curtain-like  valves  (see  Fig.  33),  whose 
upper  edges  are  attached  to  the  inner  surface  of  the  walls 
at  the  upper  margin  of  the  ventricle.  These  flaps  are 
somewhat  triangular,  and  have  strong,  white,  tendinous 
cords  extending  from  their  edges  and  under  surfaces  to 
the  walls  of  the  ventricle  below.  In  the  right  half  of  the 
heart  there  are  three  flaps,  and  this  valve  is  called  the 
tricuspid  valve.  In  the  left  side  there  are  two  flaps,  which, 
together,  make  up  the  mitral  valve.  In  the  resting  heart 


50  Physiology. 

these  flaps  hang  down  along  the  walls  of  the  ventricles  so 
•that  on  opening  the  heart  one  would  see  only  a  single 
cavity  in  each  half  of  the  heart. 

The  Aur-vent  Valves.  —  Since  these  valves  are  between 
the  auricles  and  the  ventricles  they  are  often  called  the 
auriculo-ventricular  valves.  Nearly  every  one  knows  of  the 
town  named  Pen  Mar  on  the  line  dividing  Pennsylvania 
from  Maryland.  The  meaning  of  the  name  is  clear.  And 
any  one  can  tell  wher'e  Texarkana  must  be.  So  for  con- 
venience we  shorten  auriculo-ventricular  to  aur-vent,  and 
when  speaking  of  the  aur-vent  valves  we  know,  without 
having  to  stop  and  think,  that  they  are  between  the  auricles 
and  ventricles. 

The  Semilunar  Valves.  —  From  the  base  of  the  right 
ventricle  arises  the  pulmonary  artery.  Within  its  base, 
just  as  it  leaves  the  ventricle,  are  three  pocket-like  valves, 
like  "  patch-pockets."  They  are 'in  a  circle,  with  their 
edges  touching,  and  thus  surround  the  opening,  with  their 
mouths  opening  away  from  the  heart.  A  similar  set  of 
valves  are  within  the  base  of  the  aorta,  which  arises  from 
the  left  ventricle.  Both  these  sets  of  valves  are  called 
semilunar  valves.  As  they  are  between  the  ventricles  and 
the  arteries  they  are  sometimes  called  the  ventriculo-arterial 
valves.  And  this  may  be  shortened  to  vent-art  valves. 
(See  Fig.  33-) 

Dissection  of  the  Heart. — No  description  (or  even  pictures)  can 
give  a  clear  idea  of  the  heart.  A  good  model  will  be  of  some  assist- 
ance. But  the  heart  itself  should  be  examined  carefully  and  then  dis- 
sected. The  heart  and  lungs  of  a  sheep  should  be  obtained  (ask  the 
butcher  to  save  the  "pluck,11  i.e.  the  heart  and  lungs  taken  out  together). 
The  relations  of  the  heart  to  the  lungs  and  other  organs  should  first 
be  studied,  and  then  the  pericardium  opened.  Observe  the  outside  of 
the  heart,  and  then  cut  the  heart  open  to  see  the  points  given  in  the 


Circulation  of  the  Blood. 


51 


52  Physiology. 

above  description.  After  the  heart  is  severed  from  the  lungs  the  auri- 
cles may  be  cut  off;  then,  by  pouring  water  into  the  ventricle,  the 
action  of  the  valves  between  the  auricles  and  the  ventricles  will  be 
seen.  Pressing  on  the  outer  surface  of  the  right  ventricle  will  make 
the  water  escape  through  the  pulmonary  artery.  If  this  be  split  open, 
the  semilunar  valves  at  its  base  may  be  found. 

The  Blood  Tubes  connecting  the  Heart  with  Other 
Organs.  —  The  aorta  arises  from  the  left  ventricle.  The 
pulmonary  artery  springs  from  the  right  ventricle  and 
sends  blood  to  the  lungs.  The  pre-caval  and  the  post-caval 
veins  enter  the  right  auricle.  The  pulmonary  veins,  two 
from  each  lung,  enter  the  left  auricle.  (See  Figs.  31  and  32.) 

The  Aorta.  —  The  aorta  is  the  largest  artery  in  the  body. 
.It  arises  from  the  base  of  the  left  ventricle  and  runs  a 
short  distance  toward  the  head,  then  it  arches  over  and 
runs  toward  the  lower  part  of  the  body.  The  bend,  above 
the  heart,  is  called  the  arch  of  the  aorta.  At  the  arch 
branches  are  given  off  which  supply  the  right  and  left 
arms,  and  the  right  and  left  sides  of  the  head.  Beyond 
the  arch  the  aorta  passes  behind  the  heart  and  runs  along 
the  backbone  and  passes  through  the  diaphragm.  Just 
beyond  the  diaphragm  it  gives  off  branches  to  the  liver, 
stomach,  intestine,  pancreas,  and  spleen.  It  gives  a 
branch  to  each  kidney,  and  finally  divides  into  two  large 
branches  to  the  lower  limbs.  Numerous  small  branches 
are  sent  to  other  organs ;  in  short,  the  aorta  supplies 
blood  to  every  organ  of  the  body  except  the  lungs.  (See 
Figs.  29,  30,  and  32.) 

The  Caval  Veins.  —  There  are  two  caval  veins,  the  pre- 
caval  and  the  post-caval.  The  pre-caval  brings  the  dark 
blood  from  the  head  and  arms.  It  has  four  main  branches, 
one  from  each  side  of  the  neck,  the  jugular  veins  ;  and 
one  from  each  arm,  the  subclavian  veins.  These  four 


Circulation  of  the  Blood. 


S3 


d  External  Jugular  Vein 

c  Internal  Jugular  Vein 


2  Subclavian  Artery 
ft  Subclavian  Vein 

Carotid  Artery 


i  Aorta 
in  Precaval  Vein 


iv  Postcaval  Vein 


r  Gastric  Artery 
j  Splenic  Artery 
j  Hepatic  Artery 
^  Pancreatic  Artery 


ff  Renal  Veins 
5  Renal  Arteries 


Fig.  32.    Distribution  of  Arteries  and  Veins. 


54  Physiology. 

unite  to  form  the  pre-caval  vein,  which  runs  downward  and 
enters  the  right  auricle.  The  post-caval  vein  begins  in  the 
lower  part  of  the  abdomen,  by  the  union  of  the  two  large 
veins  from  the  lower  limbs.  As  it  runs  upward,  it  receives 
branches  from  the  kidneys  and  from  the  liver;  it  passes 
through  the  diaphragm  and  enters  the  right  auricle.  (See 
Figs.  29,  30,  and  32.) 

The  Distribution  of  the  Arteries  and  Veins.  —  The  organs 
of  the  body  receive  a  supply  of  blood  in  proportion  to 
their  size  and  activity.  The  artery  supplying  the  blood  to 
any  organ  and  the  vein  which  returns  it  usually  lie  side 
by  side  (see  Fig.  32).  The  larger  arteries  are  usually 
deep-seated  and  in  protected  places. 

The  Action  of  the  Heart  —  The  heart  consists  of  muscle 
fibers  so  arranged  that  they  form  a  thick-walled  bag,  which 
stands  expanded  when  the  muscles  relax.  But  when  the 
fibers  shorten,  the  heart  contracts  and  the  blood  is  forced 
out. 

The  complete  action  of  the  heart  consists  of  three  parts, 
—  the  contraction  of  the  auricles,  the  contraction  of  the 
ventricles,  and  the  pause. 

The  Pause.  —  During  the  pause  the  blood  is  steadily 
pouring  into  the  auricles ;  into  the  right  auricle  from  the 
caval  veins,  into  the  left  auricle  from  the  pulmonary  veins. 
The  aur-vent  valves  are  now  open,  and  their  flaps  hang  loosely 
beside  the  walls  of  the  ventricles.  The  blood,  therefore, 
instead  of  stopping  in  the  auricles,  passes  on  into  the  ven- 
tricles. As  the  ventricle  fills,  the  aur-vent  valves  float  up, 
as  seen  in  the  experiment  of  pouring  water  into  the  ven- 
tricle. (See  right-hand  part  of  Fig.  33.) 

The  Contraction  of  the  Auricle.  —  When  the  ventricle  is 
full,  but  not  stretched,  and  the  auricle  partly  full,  the  auricle 


Circulation  of  the  Blood. 


55 


suddenly  contracts,  thus  forcing  more  blood  into  the  ven- 
tricle, and  distending  it.  At  the  same  time  the  aur-vent 
valves,  which  were  already  nearly  closed,  are  tightly  closed 
by  the  pressure  of  the  blood  which  is  forced  up  behind 
them.  The  flaps  of  the  valves  are  kept  from  going  up  toa 
far  by  the  tendinous  cords  and  by  the  muscles  to  which 
the  cords  are  attached. 


Auricle 


Fig.  33.    Diagram  of  the  Heart,  showing  the  Action  of  the  Valves. 

The  Contraction  of  the  Ventricle. —  Next  comes  the  con- 
traction of  the  ventricle,  slower,  but  more  powerful  than 
that  of  the  auricle.  As  the  walls  of  the  ventricle  are 
drawn  together,  they  press  upon  the  blood.  It  cannot  go 
back  into  the  auricles,  for  the  more  it  presses  against  the 
aur-vent  valves,  the  more  tightly  they  are  closed.  The 
vent-art  (semilunar)  valves  are  closed  by  back  pressure  in 
the  aorta  and  pulmonary  artery.  But  the  pressure  of  the 
blood  in  the  ventricles  is  so  much  greater  that  the  vent-art 
valves  are  forced  open,  and  the  blood  is  driven  out  of  the 
ventricles;  from  the  right  ventricle  into  the  pulmonary 
artery,  and  from. the  left  ventricle  into  the  aorta. 

While  the  ventricles  are  contracting  and  forcing  their 


56  Physiology. 

blood   out,  the  auricles  are  slowly  filling   by  the   steady 
inflow  through  the  veins. 

Systole  and  Diastole. — The  contraction  of  the  heart  is 
called  the  systole,  and  its  dilation  is  the  diastole. 

Dilation  of  the  Ventricle.  —  As  soon  as  the  ventricle  has 
completed  its  contraction  it  dilates,  and  most  of  the  blood 
that  has  accumulated  in  the  auricle  simply  falls  into  the 
ventricle.  The  dilating  ventricle  makes  a  slight  suction, 
so  the  blood  is  in  part  drawn  into  the  ventricle.  During 
the  remainder  of  the  pause  the  blood  accumulates  in  the 
ventricle  and  auricle  till  the  auricle  again  contracts  and 
the  action  is  repeated.  This  is  true  of  both  halves  of  the 
heart,  which  work  at  the  same  time,  the  two  auricles  con- 
tracting together,  and  then  the  two  ventricles.  The  right 
heart  pumps  dark  blood  while  the  left  heart  pumps  bright 
blood.  The  left  ventricle  is  thicker  walled  and  stronger 
than  the  right. 

Work  and  Rest  of  the  Heart.  —  Immediately  after  the 
contraction  of  the  auricle  comes  the  contraction  of  the 
ventricle.  The  pause  is  as  long  as  the  contractions  of 
the  auricle  and  ventricle  put  together.  In  other  words, 
the  heart  is  resting  half  the  time.  It  is  often  said  that  the 
heart  never  rests.  Its  periods  of  work  and  rest  are  so  short 
and  follow  each  other  in  such  rapid  succession  that  it  is 
hard  for  us  to  realize  that  there  is  a  resting  time  between 
each  two  beats,  and  that  this  resting  time  is  as  long  as  the 
working  time. 

Overworking  the  Heart.  —  During  violent  exercise  the 
heart  is  likely  to  be  overworked  trying  to  pump  blood 
enough  to  supply  the  overworked  muscles.  One  very 
important  part  of  training  an  athlete  is  to  strengthen  the 


Circulation  of  the  Blood.  57 

heart  by  regular  exercise  so  it  will  not  tire  out  in  pumping 
the  blood  to  the  muscles  during  an  athletic  contest,  such  as 
a  foot  race  or  boat  race. 

The  Work  of  the  Auricle.  —  The  auricle  has  three  func- 
tions: (i)  to  complete  the  filling  of  the  ventricle;  (2)  to 
complete  the  closing  of  the  aur-vent  valves ;  (3)  to  act  as  a 
reservoir  for  the  blood  entering  the  auricle  while  the  ven- 
tricle is  contracting,  that  is,  while  the  aur-vent  valves  are 
closed. 

The  Work  of  the  Ventricle.  —  The  contraction  of  each 
ventricle  forces  the  blood  around  to  the  ventricle  of  the 
other  side  of  the  heart. 

The  Sounds  of  the  Heart.  —  There  are  two  sounds  of  the 
heart :  — 

1.  A  short,  sharp  sound  made  by  the  closing  of  the 
semilunar  valves. 

2.  Just  preceding  this  sound  a  longer,  duller  sound  may 
be  heard  during  the  contraction  of  the  ventricles.     This  is 
supposed  to  be  due  to  the  vibrations  of  the  walls  of  the 
ventricles  and  of  the  aur-vent  valves. 

Action  of  the  Large  Arteries.  —  The  arteries  have  elastic 
tissue  in  their  walls.  When  the  blood  is  forced  into  them, 
they  are  stretched.  As  soon  as  the  ventricle  ceases  to  con- 
tract, and  sends  no  more  blood  into  the  arteries,  they 
"stretch  back."  We  should  not  say  contract,  for  it  is 
simply  an  elastic  reaction.  As  the  artery  reacts  it  presses 
on  the  blood,  and  hence  the  blood  tries  to  escape  in  every 
possible  way.  It  cannot  go  back  into  the  ventricles,  for  it 
fills  the  pockets  of  the  semilunar  valves,  and  closes  them 
with  a  click.  The  blood  therefore  flows  along  the  arteries, 
through  the  pulmonary  artery  to  the  lungs,  and  through 

5 — PHY 


Physiology. 


the  aorta  and  its  branches  to  all  the  other  parts  of  the 
body. 

The  elastic  reaction  of  the  arteries  thus  helps  to  make 
steady  the  flow  of  blood,  which  is  jerky  as  it  leaves  the 
heart. 

Variation  of  the  Amount  of  Blood  needed.  —  Each  organ 
requires  a  supply  of  blood  in  proportion  to  its  activity. 
An  actively  working  organ,  like  the  brain,  demands  much 
more  blood  than  does  such  an  inactive  organ  as  a  bone. 
Further,  the  working  tissues,  such  as  the  brain  and  mus- 
cles, need  a  great  deal  more  blood  while  they  are  at  work 
than  when  they  are  resting.  An  organ  needing  a  large 
supply  of  blood  all  the  time  might  secure  this  by  having  a 
large  artery.  But  how  can  the  supply  be  regulated  so  that 
an  organ  may  receive,  now  more,  now  less,  according  to  its 
needs  ? 

Plain  Muscle  Fibers  in  the  Walls  of  the  Arteries.  —  This 
is  regulated  by  the  medium-sized  and  small  arteries  leading 

to  the  parts.  In  the  walls  of  these 
arteries  are  plain  muscle  fibers. 
They  are  arranged  circularly  in  the 
walls  of  the  arteries  (see  Fig.  36). 
These  fibers  have,  like  all  muscle 
fibers,  the  power  of  shortening. 
When  they  shorten  they  reduce 
the  size  of  the  artery,  and,  there- 
fore, for  the  time,  less  blood  can 
flow  through  it.  When  the  muscle 
fibers  relax,  the  artery  widens,  and 
allows  more  blood  to  pass  through  it. 


Nucleus 


Isolated   Fibers 


Fibers  Joined 


Fig.  34.     Plain  Muscle  Fibers. 


Illustration  of  the  Action  of  Muscles  in  Arterial  Walls.  —  To  illus- 
trate the  action  of  the  muscles  in  the  walls  of  an  artery,  let  the  water 


Circulation  of  the  Blood. 


59 


rim  through  a  hose  or  large  rubber  tube.     Now.  if  a  row  of  persons  take 
hold  of  this  tube,  the  grip  of  their  hands  is  like  that  of  the  muscles. 


Connective  Tissue 


Endothelium 


Nucleuses 


Muscle  Fiber 


Fig.  35.    Plain  Muscle  Fiber.    Separate  and  in  Wall  of  Artery. 


When  the  hands  tighten  their  grip,  the  size  of  the  hole  in  the  tube  is 
made  smaller,  and  less  water  is  allowed  to  flow  through  it.  When  the 
hands  relax,  the  tube,  being  elastic, 
allows  more  liquid  to  flow  through  it. 

Endothelium 

Illustration  of  a  Small  Artery. — 
To   represent  a  small  artery,  take  a   internd  Elastic 
small,    thin-walled    rubber   tube    and 
wind  a  red  thread  around  it.     Now,  if    circular  Mus- 
the  thread    could    shorten,   it  would      cl°  Fibers 
make  the  tube  smaller. 

The  Action  of  Plain  and  Striated 
Muscles     Fibers     compared.  —  These 
plain   muscle  fibers  are    further  like 
those  of  the  skeletal  muscles  in  that   The  Outer 
they  are   under    the   control   of   the      Coat 
nerves,   but  they  are  involuntary  in   . 

their    action.      We    cannot    interfere      Fig.  36.    coats  of  a  Small  Artery, 
with  the  action  of  these  muscles,  no 

matter  how  strongly  we  may  will  to  do  so.     Without  our  thinking  about 
it,  more  blood  goes  to  the  muscles  of  the  legs  when  we  walk,  more  to 


6o 


Physiology. 


the  brain  when  we  are  studying,  to  the  digestive  organs  after  eating,  etc. 
The  plain  muscle  fibers  shorten  at  a  much  slower  rate  than  the  striated 

fibers.    They  are  also  slower  in  relaxing. 

Circulation  of  Blood  in  the  Web  of  a 
Frog's  Foot.  — This  is  a  beautiful  sight. 
Here  you  may  see,  under  the  microscope, 
the  active  streams  of  blood.  Small  ar- 
teries divide  to  form  capillaries,  and  capil- 
laries unite  again  to  form  the  small  veins. 
In  the  narrow  capillaries  the  corpuscles 
may  be  seen  moving  along  in  single  file, 
with  barely  width  enough  to  pass  through 
the  slender  tube.  If  you  see  this  in  the 
frog's  foot,  you  can  understand  how  the 
blood  flows  through  all  the  active  tissues 
of  your  body.  (See  Figs.  37  and  39.) 

the    Capillaries.  —  The 


Fig.  37.  "  Capillary  Blood  Tubes  in 
the  Web  of  a  Frog's  Foot,  under 
a  Low  Power  of  a  Microscope." 
From  Hall's  "  Physiology." 


arteries 


The    Blood    Flow    in 

divide   and    subdivide,    and  surface  view 

become  capillaries,  which 
have  connecting  branches, 
forming  a  close  network 
of  tiny  thin-walled  tubes. 
These  penetrate  nearly 
every  tissue  of  the  body. 
The  blood  cannot  do  its  full 
work  till  it  is  in  the  tissues, 
and  to  reach  the  tissues  it 
must  soak  through  the  walls 
of  the  capillaries.  The  Fig.  38. 
work  of  the  heart  and  ar- 
teries is  to  keep  a  slow  and  steady  flow  of  blood  through 
the  capillaries,  that  the  tissues  may  be  constantly  supplied. 

The  Veins. — The  capillaries,  after  penetrating  the  tis- 
sues, unite  again  to  form  small  veins,  which  in  turn  unite 
to  form  larger  ones,  till  finally  two  great  veins,  the  pre- 


Longitudinal  Section 

Capillaries,  composed  of  a  Single 
Layer  of  Cells. 


Circulation  of  the  Blood. 


61 


caval  from  the  upper  and  post-caval  from  the  lower  part  of 
the  body,  return  the  blood  to  the  heart.     The  veins,  like 


Walls  of  Capillaries 


Tissues  of  Web 


Fig.  39.     Part  of  Frog's  Web  (highly  magnified). 

the  arteries,  are  smooth  inside  and  elastic  (though  less 
elastic  than  the  arteries).  They  are  thinner-walled  than 
the  arteries  (see  Fig.  40)  and  collapse  when  empty, 


62 


Physiology. 


Vein 


Artery 


Fig.  40. 


whereas   the    larger   arteries    stand  open,   after  they  are 
emptied  of  blood.     There   are  many  cross-branches  unit- 
ing veins,  so  that  if  the  flow 
is  stopped  in  one  vein,  the 
blood    can    take    a    "  cross- 
road"   into     another     large 
vein.      This  cross-branching 
may  usually  be  seen  on  the 
Uj^Mp^H  back  of  the  hand. 

"\HJfc~    .fliP  The  Valves  in  the  Veins. 

—  The    only    valves    in    the 
arteries  are  those"  at  the  be- 

Cross-section^of  Small  Artery      ginnjng  of  the  aorta  and   pul- 

monary  artery.     Ma.ny  of  the 

veins  have  similar  pocket-like  valves  though  less  strong 
than  those  of  the  arteries.  They  are  usually  in  pairs,  but 
sometimes  single  or  in  threes.  They  all  have  the  mouths 
of  the  pockets  toward  the  heart,  so  that  the  blood  flows 
freely  toward  the  heart,  but  is  kept  from  flowing  the  other 
way  on  account  of  the  filling 
of  the  valves  by  the  back 
pressure  of  the  blood.  When 
the  blood  is  flowing  through 
the  veins  toward  the  heart, 
the  valves  lie  against  the  walls 
of  the  veins  (see  Fig.  41). 

Illustration  of  Valves  in  the  Veins. 

—  Make  a  cloth  tube  (or  take  the      Open  Shut 

lining  of  a  boy's  coat  sleeve)  and  Fig.  41.    Vaives  of  the  Veins, 

sew  three  patch-pockets  on  the  in- 
side, in  a  circle,  z.£.  with  edges  touching  each  other.     Make  the  pockets 
a  little  "full."      Pour  sand,  shot,  or  grain  through  the  sleeve  first  in 
one  direction  and  then  in  the  other.     This  shows  how  the  valves  fill 
and  block  the  passage  when  there  is  back  pressure  of  the  blood. 


Circulation  of  the  Blood.  63 

Evidences  of  Valves  in  Our  Veins.  —  i.  With  the  forefinger  stroke 
one  of  the  veins  on  the  hand  or  wrist  toward  the  tips  of  the  fingers. 
The  veins  swell  out.  The  blood  meets  resistance  in  the  valves  of  the 
vein.  Their  location  may  be  determined  by  their  bulging  out  during 
the  experiment. 

2.  Stroke  a  vein  toward  the  body,  and  the  blood  is  pushed  along 
without  resistance. 

3.  Let  the  left  hand  hang  by  the  side.     Note  the  large  vein  along 
the  thumb  side  of  the  wrist.     Place  the  tip  of  the  second  finger  on  this 
vein  just  above  the  base  of  the  thumb.     Now,  while  pressing  firmly 
with    the   tip  of  the   second  finger,  let  the  forefinger,  with  moderate 
pressure,  stroke  the  vein  up  the  wrist.     It  may  be  seen  that  the  blood 
is  pushed  on  freely,  but  comes  back  only  part  way.     It  stops  where  it 
reaches  the  valves,  filling  the  vein  full  to  this  point,  but  leaving  it  col- 
lapsed beyond,  as  shown  by  the  groove.     Remove  the  second  finger, 
and  the  vein  immediately  fills  from  the  side  nearer  the  tip  of  the  fingers. 

These  experiments  show  that  the  blood  in  the  veins  moves  freely 
toward  the  body,  but  cannot  flow  outward  to  the  extremities. 

Effect  of  Pressure  on  the  Veins.  —  Since  the  valves  in 
the  veins  open  toward  the  heart,  any  alternating  pressure 
on  the  veins  helps  to  push  the  blood  on  toward  the  heart. 
The  valves  are  most  numerous  in  the  veins  near  the  sur- 
face and  in  the  veins  of  the  muscles.  The  pressure  of  the 
muscles  during  their  action  (thickening  while  shortening) 
produces  pressure  on  the  veins ;  and  as  the  muscles  act 
for  a  short  time  only,  and  then  relax,  this  alternate  com- 
pression and  release  aids  very  much  in  moving  the  blood 
on  toward  the  heart. 

How  the  Muscles  help  the  Heart.  —  This  effect  is  greater 
at  the  time  the  muscles  need  the  most  active  circulation ; 
namely,  when  they  are  in  action,  and  are  using  the  most 
blood.  The  heart  has  power  enough  to  pump  the  blood 
clear  around  from  each  ventricle  to  the  auricle  of  the  other 
side  of  the  heart ;  but  this  outside  aid  comes  in  good  play 
to  relieve  the  heart  at  a  time  when  it  has  an  unusual 


64  Physiology. 

amount  of  work  to  do,  as  when  one  is  using  a  large  num- 
ber of  muscles  vigorously. 

"  Every  active  muscle  is  a  throbbing  heart,  squeezing 
its  blood  tubes  empty  while  in  motion,  and  relaxing  so 
as  to  allow  them  to  fill  up  anew." 

Rate  of  Blood  Flow  in  the  Arteries  and  Capillaries.  —  The 

blood  flows  rapidly  in  the  arteries,  slowly  in  the  capillaries. 
Why  is  this  ?  When  an  artery  divides,  the  two  branches 
taken  together  are  larger  than  the  one  artery  that  divided 
to  form  them.  Hence  as  the  blood  flows  on  it  is  continu- 
ally entering  a  wider  and  wider  channel ;  for  if  all  the  cap- 
illaries fed  by  the  aorta  were  united  they  would  make  a 
tube  several  hundred  times  as  large  as  the  aorta. 

The  Flow  of  the  Blood  compared  with  the  Current  of  a 
Stream.  —  If  we  walk  along  a  stream,  we  see  that  the 
channel  keeps  changing  in  width  and  depth.  Where  the 
channel  is  large,  whether  from  increased  width  or  depth, 
there  the  current  is  slower,  but  wherever  the  channel  is 
reduced,  the  current  is  more  rapid.  So  the  stream  in  the 
comparatively  narrow  artery  is  swift.  In  the  capillaries, 
although  any  single  channel  is  small,  these  channels  all 
together  are  wide ;  the  result  is  the  same  whether  a  river 
widens  out  into  a  single  lake,  or  divides  into  a  great  num- 
ber of  channels  running  past  many  islands. 

The  Flow  of  Blood  in  the  Veins.  —  When  two  veins  unite, 
the  one  vein  they  form  is  not  quite  equal  to  the  sum  of  the 
two ;  so  when  the  blood  gathers  in  the  veins  it  is  really  en- 
tering a  narrower  channel,  and  it  flows  faster.  And  it 
keeps  gaining  in  speed  till  it  reaches  the  heart. 

Flow  in  Arteries  and  Veins  compared.  —  Although  the 
blood  keeps  flowing  fast  as  it  gets  nearer  the  heart  in  the 


Circulation  of  the  Blood. 


caval  veins,  it  does  not  go  as  fast  as  when  it  left  the  heart 
in  the  aorta,  for  there  are  two  caval  veins  each  about  as 
large  as  the  aorta. 


Pulmonary  Vein 


Digestive  Tube 


Pulmonary  Artery 

Lymph  Vein 

~  Right  Auricle 
-  Right  Ventricle 
Caval  Vein 

Liver 


Fig.  42.     Plan  of  Circulation.    (Back  View.) 

Rate  of  Flow  in  Arteries,  Capillaries,  and  Veins.  —  The 
blood  flows  rapidly  in  the  arteries,  slower  in  the  veins,  and 
slowest  in  the  capillaries. 

Summary. —  i.   The  heart  beats  about  seventy-two  times  a  minute. 

2.  The  pulse  is  a  wave  running  along  an  artery. 

3.  The  pulse  varies  with  age,  health,  food,  etc. 

4.  The  heart  has  two  main  cavities,  one  in  each  half  of  the  heart,  and 
two  separate  streams  are  flowing  through  it. 


66  Physiology. 

5.  Valves  allow  the  blood  to  flow  through  the  heart  in  one  direc- 
tion, but  prevent  its  return. 

6.  The  heart  is  a  hollow  muscle,  and  by  contraction  forces  the 
blood  out  into  the  arteries. 

7.  The  heart  works  about  half  the  time. 

8.  The  large  arteries,  by  elastic  reaction,  push  the  blood  on  while 
the  heart  is  resting. 

9.  Circular  muscle  fibers  in  the  walls  of  the  medium-sized  arteries 
regulate  the  blood  supply  to  the  organs. 

10.  In  the  arteries  the  blood  flow  is  rapid  and  jerky,  in  the  capillaries 
slow  and  steady. 

11.  The  thin  walls  of  the  capillaries  allow  the  liquid  part  of  the 
blood  to  soak  out  and  nourish  the  tissues,  and  to  soak  back  into  the 
capillaries  bearing  waste  matter. 

12.  The  veins  are  thin  walled,  and  collapse  when  empty,  while  the 
arteries  are  thick  walled,  and  stand  open  when  empty  of  blood. 

13.  Arteries  carry  blood  from  the  heart,  while  veins  carry  it  toward 
the  heart. 

14.  The  veins  have  valves  which  allow  the  blood  to  pass  toward 
the  heart,  but  not  away  from  it. 

15.  Any  alternating  pressure  on  the  veins  aids  the  blood  flow. 

1 6.  The  blood  flow  is  most  rapid  in  the  arteries,  slower  in  the  veins, 
slowest  in  the  capillaries.     . 

17.  Gravity  influences  circulation. 

Questions.  —  i .    Why  do  the  large  arteries  lie  deep  ? 

2.  In  which  direction  should  the  limbs  be  stroked  to  aid  circulation  ? 

3.  How  does  slapping  the  hands  around  the  body  warm  the  fingers  ? 

4.  How  can  a  horse  or  a  cow  be  comfortable  with  the  head  down  ? 

5.  Why  are  the  walls  of  the  left  ventricle  thicker  than  those  of  the 
right? 

6.  Trace  a  drop  of  blood  from  the  tip  of  a  finger  around  the  circuit 
to  the  same  point  again. 

7.  Does  the  pulse  at  the  wrist  occur  at  exactly  the  same  time  as  at 
the  temple  ?     Or  at  the  same  time  as  the  heart-beat  ? 


CHAPTER   VII. 
CONTROL  OF  CIRCULATION. 

Circulation  controlled  by  the  Nervous  System.  —  We 
know  that  fear  often  causes  the  face  to  turn  pale  and  that 
shame  makes  it  red.  Certain  emotions  also 
quicken  or  retard  the  action  of  the  heart. 
Great  grief  or  joy  has  caused  sudden  death 
by  stopping  the  action  of  the  heart. 

Nervous    Control    Involuntary. 
—  But  this  control  is  not  volun- 
tary.      The  will  has  nothing  di- 
rectly to  do  with  it.     We  often  wish  to  keep 
from  getting  red  in  the  face  when  embar- 
rassed, but  cannot  prevent  it.     Neither  can 
we  keep  from  turning  pale  through  fright 
or  pain.     We  cannot  keep  the  heart  from 
beating  faster  when  we  are  excited.     Instead 
of  being  controlled  by  the  brain,  circulation 
is  chiefly  under  the  control  of  a  special  part 
of  the  nervous  system,  known  as  the  Sym- 
pathetic Nervous  System. 

The  Sympathetic  Nervous  System. — The 

sympathetic  nervous  system  consists  of  two 

rows  of  ganglions  in  the  body  cavity,  one  p.g  43    Ffont  View 

along  each   side  of  the   spinal  column,  re-   of  spinal  cord  with 

.    .  i  i  r  i  Sympathetic  Gancr- 

ceiving   branches   from   the   spinal  nerves,    lions  of  one  side. 

67 


Carotid  Plexus 


Superior  Cervical  Ganglion    - 


Middle  Cervical  Ganglion 


Pharyngeal  Branches 
Cardiac  Branches 

Deep  Cardiac  Plexus 

Superficial  Catdiac  Plexus 


Solar  Plexus 


Aortic  Plexus 


Lumbar  Ganglions 


Fig.  44.    Vertical  Section  of  Body,  showing  Sympathetic  Nerves  and  Ganglions  of  Right 
Side  and  their  Connection  with  the  Ce re bro- spinal  Nerves. 


Control  of  Circulation. 


Spinal  Cord 


Sympathetic 
Ganglion 


Fig.  45-    Ideal  Cross-section  of  the  Nervous 
System.    (After  Landois  and  Stirling.) 


and  sending  branches  to  the  heart  and  lungs  in  the  chest, 
and  to  the  liver,  stomach,  and  other  organs  in  the  abdomen. 
In  many  places  these  nerves  form  a  thick  network  called 
a  plexus.  One  very  large  plexus  on  the  dorsal  surface  of 
the  stomach  is  called  the  solar  plexus.  (See  Fig.  44.) 

Regulation  of  the  Size  of  the  Arteries.  —  In  the  last  chap- 
ter we  learned  that  in  the  walls  of  the  arteries  are  muscle 

fibers  having  a  ring-like 
arrangement.  When  these 
muscle  fibers  shorten  they 
make  the  artery  narrower, 
and  less  blood  can  flow 
through  it.  When  the 
muscle  fibers  relax,  they 
lengthen ;  the  artery  be- 
comes wider,  and  more 
blood  flows  through  it.  Now  these  muscle  fibers  are  under 
the  control  of  the  sympathetic  nerves.  The  sympathetic 
nerves,  therefore,  regulate  the  amount  of  blood  that  goes 
to  every  organ. 

Blushing. — The  sudden  reddening  of  the  face  means 
that  more  blood  is  flowing  through  the  skin  of  the  face. 
The  arteries  by  which  blood  reaches  the  face  have  quickly 
widened,  and  this  is  because  the  muscle  fibers  in  the  walls 
of  the  arteries  have  suddenly  relaxed.  To  go  still  further 
back  in  the  explanation,  some  emotion  has  started  nerve 
currents  which  travel  along  the  fibers  of  the  sympathetic 
nerves  and  caused  the  arteries  to  widen. 

Sudden  Pallor. —  On  the  other  hand,  if  the  muscle  fibers 
in  the  walls  of  the  arteries  suddenly  shorten,  the  face  will 
turn  pale,  because  less  blood  flows  in  the  skin  of  the  face. 
Such  a  change,  as  before,  is  due  to  the  nerve  currents 


7° 


Physiology. 


Synnoathetic  Nejve  Chains 

GRAY    \ 
MATTER       *> 


brought  by  the  sympathetic  nerves.  Of  course  the  face 
may  turn  pale  as  the  result  of  the  stopping,  or  checking, 
of  the  action  of  the  heart,  as  in  ordinary  fainting. 

Ordinary  Changes  in  Blood  Flow. — Without  going  to  the 
extreme  of  pallor  and  blushing,  the  color  of  the  face  varies, 
under  the  control  of  the  sympathetic  nerves.  All  the  or- 
gans of  the  body  receive  now  more,  now  less,  blood,  accord- 
ing as  they  need  it.  And  all  this  variation  in  blood  supply 
is  regulated  by  the  sympathetic  nervous  system. 

Effect  of  Exercise  on  the  Size  of  the  Arteries.  —  When 
the  muscles  work,  of  course  they  need  more  blood.  To 
give  them  more  blood  the 
arteries  widen.  When  one 
is  exercising  actively,  the 
muscles  take  so  much  blood 
that  we  should  not 

Dorsal  Root 

expect   the  brain  or     sPmai  Nerve 
the  digestive  organs     Ventral  Root 
to  do  much  work,  for  there 
is  only  a  certain  amount  of 
blood  in  the  body,     Hence  if 
one  organ,  or  set  of  organs, 

getS     more     blood,     the     Other     Fig.  46.      Relation   of  Spinal   Cord   and 

Sympathetic  Nervous  System. 

organs    must,    for   the    time, 

receive  less.     Therefore  we  see  why  we  should  rest  after 

eating,  both  from  muscular  as  well  as  from  mental  work. 

How  the  Heart  is  made  to  Beat  Faster.  —  When  many 
large  muscles  are  at  work,  it  is  not  enough  merely  to  widen 
the  arteries.  This  would  allow  more  blood  to  go  to  them, 
but  would  not  send  them  as  much  as  they  need.  The 
heart  must  beat  faster,  or  with  more  force,  or  both.  And 
the  heart  is  made  to  beat  faster  and  stronger  by  the  nerve 


.   Ganglion  of 
Dorsal    R.oot 


Sympathetic 
Ganglion 


Control  of  Circulation. 


71 


currents  that  it  receives  through,  the  sympathetic  nerves. 
When  we  exercise  actively,  the  fact  that  the  muscles  need 
more  blood  is  telegraphed  both  to 
the  heart  and  to  the  arteries  leading 
to  the  muscles  of  the  arteries,  and 
they  are  regulated  accordingly. 

How  the  Heart  is  made  to  Beat 
Slower.  —  The  slowing  of  the  beat  of 
the  heart  is  due  to  other  nerves,  not 
belonging  to  the  sympathetic  system. 
The  vagus  nerves  are  a  pair 
of  cranial  nerves.     They  arise 
from  the  sides  of   the    spinal 
bulb,  at  the  base  of  the  brain, 
and,   passing    downward,   give 
branches  to  the  gullet,  stomach, 
lungs,  and  heart.     The  distri- 
bution of  the  vagus  nerves  is 
shown  in  Fig.  47.     Nerve  cur- 
rents reaching  the  heart  through  the 
vagus  nerves  make  it  beat  slower, 
and  if  the  current  is  strong  enough, 
as  in  case  of  a  severe  blow  over  the 
stomach,  may,  by  reflex  action,  stop 
the  heart. 


Lungs 


Heart 


Liver 


Stomach 


Fig.  47. 


Distribution  of  Vagus 
Nerve. 


Influence  of  Gravity  on  Circulation.  —  Although  the  heart 
pumps  the  blood  around  through  the  body  in  spite  of 
the  force  of  gravity,  yet  the  circulation  is  influenced  by  this 
force.  For  instance,  a  person  who  has  fainted  should  be 
laid  flat  on  his  back,  that  the  heart  may  more  easily  drive 
blood  to  the  brain.  A  sore  hand  feels  less  pain  if  held  up, 
as  in  a  sling,  than  when  hanging  by  the  side,  and  a  sprained 


72  Physiology. 

ankle  does  better  rested  on  a  chair,  as  less  blood  flows  to  it. 
Nearly  every  one  has  noted  the  pain  following  the  pressure 
of  blood  when  a  sore  hand,  or  foot,  is  suddenly  lowered. 

Experiments  illustrating  the  Effect  of  Gravity  on  Circulation.  —  Let 

the  pupils  stand.  Let  one  arm  hang  freely  by  the  side.  Hold  the  other 
arm  straight  up  as  far  as  the  clothing  will  readily  permit.  Observe  :  — 

1.  The  difference  in  the  color  of  the  two  hands. 

2.  The  difference  in  fullness,  both  in  the  feeling  of  fullness  and  in 
the  projection  of  the  veins. 

3.  The  difference   in  temperature ;    place  the  backs  of  the  hands 
against  the  cheeks. 

The  position  largely  regulates  the  amount  of  blood  in  the  hand,  and 
the  amount  of  blood  regulates  the  temperature,  the  size,  and  the  color. 

Clothing  and  Circulation.  —  No  part  of  the  clothing 
should  be  tight  enough  to  interfere  with  the  circulation. 
Such  interference  is  perhaps  most  frequent  in  our  foot 
wear.  In  cold  weather  tight  shoes  keep  the  feet  cold 
and  may  result  in  their  freezing,  while  the  same  thickness 
of  covering,  if  loose,  would  be  comfortable.  Men  often 
wear  hats  too  tight ;  this  probably  leads  to  baldness.  Tight 
garters  sometimes  hinder  circulation  and  cause  cold  feet. 

Congestion.  —  Congestion  is  an  unnatural  temporary  col- 
lection of  blood  in  any  part  or  organ.  This  may  be  merely 
for  a  short  time,  and  no  serious  harm  results  from  it.  But 
if  it  is  long  continued,  it  may  do  great  harm. 

Inflammation.  —  If  the  congestion  becomes  permanent, 
we  call  it  inflammation.  That  is,  it  is  a  permanent  over- 
supply  of  blood,  which  may  bring  many  bad  results. 
There  is  usually  redness,  pain,  and  often  swelling.  We 
have  all  seen  such  a  condition  around  a  boil  or  a  wound. 

Use  of  Mustard  Plaster.  —  Mustard  applied  to  the  skin 
causes  irritation.  It  makes  the  skin  red.  This  means  that 
more  blood  is  drawn  into  the  skin  through  the  action  of 


Control  of  Circulation.  73 

the  sympathetic  nerves  on  the  muscles  in  the  walls  of  the 
arteries.  If  there  is  more  blood  in  the  skin,  there  must  be 
less  somewhere  else  at  the  same  time.  Now  this  is  what 
makes  a  mustard  plaster  useful.  When  there  is  congestion 
or  inflammation  in  some  internal  organ,  a  mustard  plaster 
applied  to  the  outside  draws  away  some  of  the  blood  and 
thus  affords  relief  to  the  congested  part. 

The  Hot  Foot  Bath.  —  When  one  has  a  cold,  a  hot  foot 
bath  relaxes  the  arteries  of  the  feet.  This  is  a  good  means 
of  drawing  the  blood  away  from  internal  organs,  and  often 
saves  the  person  from  serious  or  even  fatal  results  from 
a  bad  cold. 

Summary.  —  i.   Circulation  is  controlled  by  the  nervous  system. 

2.  This  control  is  involuntary. 

3.  The  sympathetic  nervous  system  consists  of  two  rows  of  ganglions 
in  the  body  cavity  along  each  side  of  the  spinal  cord. 

4.  The  sympathetic  system  regulates  the  size  of  the  arteries,  and  by 
this  means  regulates  the  amount  of  blood  going  to  any  organ. 

5.  The  heart  may  be  made  to  beat  faster  through  the  sympathetic 
nervous  system.     This  may  come  through  reflex  action  and  be  caused 
by  emotions. 

6.  The  heart  may  be  made  to  beat  slower  through  the  vagus  nerves. 

Questions.  —  i.   Why  do  the  feet  easily  get  cold  while  studying? 

2.  What  makes  the  hands  grow  red  and  puff  up  after  snowballing? 

3.  Why  does  light  exercise  before  retiring  make  one  sleep  better? 

4.  How  does  the  application  of  ice,  or  cold  water,  relieve  headache? 

5.  Why  should  the  clothing  be  changed  after  getting  wet? 


6 — PHY 


CHAPTER   VIII. 
THE   BLOOD  AND  THE  LYMPH. 

The  Blood.  —  The  blood  is  composed  of  a  clear  liquid, 
the  plasma,  and  the  blood  cells,  or  corpuscles.  In  a  drop 
of  blood  under  the  microscope  tne  plasma  occupies  the 
clear  spaces  between  the  corpuscles.  The  corpuscles 
make  up  one  third  of  the  bulk  of  the  blood,  and  the 
plasma  two  thirds. 

Microscopic  Examination  of  the  Blood.  —  To  get  a  drop  of  blood 
from  the  finger,  wind  a  cord  around  the  finger,  beginning  at  the  base, 
drawing  the  cord  moderately  tight,  until  the  last  joint  is  reached.  By 
this  time  the  end  of  the  finger  is  usually  well  distended  with  blood. 
With  a  clean  needle  make  a  quick,  sharp,  light  puncture  near  the  base 
of  the  nail ;  this  ordinarily  brings  a  drop  of  blood.  Put  a  very  small 
drop  on  each  of  several  slides  and  quickly  cover  with  coverslips. 
Examine  with  a  high  power. 

The  Colored  Corpuscles.  —  These  are  often  called  the 
red  corpuscles.  Although  in  the  mass  they  give  the  blood 
a  red  appearance,  when  seen  singly  they  are  faint  yellow- 
ish red.  In  shape  they  are  seen  to  be  circular  disks, 
hollowed  on  each  side  like  a  sunken  biscuit.  These  cor- 
puscles tend  to  gather  side  by  side,  in  rolls,  like  coins. 
Each  colored  corpuscle  is  a  cell  without  a  nucleus. 

The  Colorless  Corpuscles.  —  In  the  open  spaces  between 
the  rolls  of  colored  corpuscles  may  occasionally  be  found 
some  spherical  corpuscles.  They  are  often  called  the 
white  corpuscles.  The  colorless  corpuscles  are  very  numer- 

74 


The   Blood  and  the   Lymph.  75 

ous  around  a  wound.     They  seem   to  help  in    repairing 
tissues. 


White  Corpuscles 


HIGHLY    MAGNIFIED 


White  Corpuscle   ...± 


Red  Corpuscles 
in  Rolls 


MODERATELY   MAGNIFIED 
Fig   48.    Red  and  White  Corpuscles  of  the  Blood. 

The  Plasma.  —  The  plasma  consists  chiefly  of  water, 
having  in  solution  various  salts,  including  common  salt; 
it  also  contains  the  nourishing  materials  for  the  tissues. 
These  nourishing  materials,  obtained  from  the  food  by 
digestion,  consist  chiefly  of  proteids,  fats,  and  sugar.  The 
plasma  also  contains  waste  matters  from  the  working  tis- 
sues on  their  way  out  of  the  body. 

The  Color  of  Blood.  —  The  difference  in  color  of  a  single 
corpuscle  and  the  blood  in  the  mass  may  be  better  under- 
stood by  comparing  it  with  something  that  we  see  more 
frequently.  A  tumbler  of  currant  jelly  has  a  rich,  red 


76  Physiology. 

color,  but  a  thin  layer  of  the  same  jelly,  as  when  one  takes 
a  spoonful  on  a  plate,  has  a  pale  color,  more  yellowish. 
The  colorless  plasma  with  the  colored  bodies  in  it  may  be 
compared  to  a  glass  dish  filled  with  cranberries  and  water. 

Hemoglobin.  —  The  coloring  matter  in  the  blood,  then, 
is  wholly  in  the  colored  corpuscles.  Examination  of  these 
corpuscles  shows  that  their  color  is  due  to  a  substance 
called  hemoglobin.  The  hemoglobin  in  the  corpuscles  is 
the  chief  agent  in  picking  up  the  oxygen  from  the  air  in 
the  lungs  and  carrying  it  to  the  tissues  in  the  body. 

The  Coagulation  of  Blood.  —  When  the  blood  escapes 
from  its  natural  channels  it  usually  changes  from  a  liquid 
to  a  jelly-like  condition.  This  is  known  as  coagulation. 
It  is  due  to  the  formation  of  threads  of  fibrin  from  the 
plasma.  These  threads  of  fibrin  entangle  and  inclose  the 
corpuscles,  and  the  two  constitute  the  clot.  The  liquid 
that  afterward  separates  from  the  clot  is  the  serum,  and 
differs  from  the  plasma  only  in  the  absence  of  the  fibrin, 
which  is  exceedingly  small  in  quantity,  though  of  great 
importance  in  its  action.  Coagulation  often  serves  to  stop 
the  flow  of  blood  from  wounds. 

Fibrin.  —  If  freshly  drawn  blood  be  stirred  rapidly  with 
a  little  roll  of  wire  screen,  there  will  soon  collect  on  the 
wires  a  stringy  substance.  Thorough  washing  will  soon 
leave  this  colorless.  It  is  fibrin.  If  the  stirring  has  been 
done  thoroughly,  the  blood  will  no  longer  clot,  no  matter 
how  long  it  may  stand. 

Watching  Coagulation.  —  If  you  have  a  slight  cut  on  the 
hand,  it  will  pay  to  watch  the  changes  in  the  blood.  First 
it  is  a  red  liquid.  Then  it  becomes  jelly-like.  Then  a 
clear  or  yellowish  liquid  comes  out ;  this  is  serum.  The 
serum  evaporates  and  the  dried  clot  forms  a  scab. 


The  Blood  and  the  Lymph.  77 

Liquid  Blood  and  Coagulated  Blood.  —  The  following 
scheme  shows  the  difference  between  the  liquid  blood  and 
the  coagulated  blood :  — 


Liquid  Blood 


Plasma  .      .    f  Serum 


Corpuscles 


Clot 


Coagulated  Blood. 


"  Black-and-blue  "  Spots.  —  A  bruise  often  breaks  some 
of  the  capillaries  without  breaking  the  skin.  Blood  escapes 
into  the  spaces  in  the  skin  or  under  it.  This  blood  clots, 
and  the  dark  color  shows  through  the  skin.  This  clotted 
blood  is  gradually  absorbed  and  the  color  disappears. 

Amount  of  Blood.  —  The  blood  constitutes  about  one 
thirteenth  of  the  weight  of  the  body.  In  a  body  weighing 
one  hundred  and  fifty  pounds  this  would  be  about  six 
quarts. 

Quantity  of  Blood  in  Different  Organs.  —  i.  One  fourth 
is  in  the  heart  and  the  larger  arteries  and  veins  (including 
those  of  the  lungs). 

2.  One  fourth  in  the  liver. 

3.  One  fourth  in  the  skeletal  muscles. 

4.  One  fourth  in  the  other  organs. 

The  Lymph  Spaces.  —  We  have  seen  that  the  capillaries 
have  very  thin  walls.  Through  their  walls  part  of  the 
plasma  of  the  blood  soaks  out,  and  is  then  called  lymph. 
It  passes  into  irregular  cavities  in  the  tissue  called  lymph 
spaces.  Most  of  these  lymph  spaces  are  minute  chinks  or 
crevices  in  the  connective  tissue  of  the  different  parts  of 
the  body. 

The  Lymph  Tubes.  —  Opening  out  of  the  lymph  spaces 
are  irregular  passage-ways  called  lymph  capillaries,  and 


78  Physiology. 

these  lymph  capillaries  are  continuous  with  larger  but 
still  thin-walled  lymph  tubes,  called  lymph  veins.  But, 
unlike  the  blood  veins,  the  lymph  veins  do  not  gradually 
increase  in  size  by  uniting.  They  suddenly  form  a  large 
tube,  the  receptacle  of  the  chyle,  beginning  in  the  upper 
part  of  the  abdomen.  (See  Figs.  50  and  81.) 

The  Main  Lymph  Duct.  —  This  tube  soon  narrows  and 
passes  through  the  diaphragm,  close  to  the  spinal  column, 
and  up  along  the  column  near  the  aorta,  and  empties  into 
the  veins  of  the  neck  at  the  junction  of  the  left  jugular 
and  left  subclavian  veins.  This  tube  is  the  "thoracic 
duct,"  or  the  main  lympJi  duct.  It  has  numerous  valves, 
and,  like  some  of  the  smaller  lymph  veins,  it  presents  a 
beaded  appearance,  due  to  the  filling  and  bulging  out  of 
the  valves.  In  the  right  side  of  the  neck  is  a  short  right 
lymph  duct,  which  receives  lymph  from  the  right  side 
of  the  head,  neck,  and  thorax,  and  from  the  right  arm. 
The  lymph  tubes,  as  a  whole,  are  usually  called  the 
"lymphatics."  (See  Figs.  50  and  81.) 

Valves  at  the  Mouth  of  the  Lymph  Tubes.  —  There  are 
valves  where  these  lymph  ducts  empty  into  the  veins  which 
prevent  any  reflow  of  liquid  into  the  ducts,  but  allow  the 
lymph  to  pass  freely  into  the  veins. 

Muscle  Fibers  in  the  Walls  of  the  Lymph  Tubes.  —  There 
are  plain  muscle  fibers  in  the  walls  of  the  lymph  ducts. 

Lymphatic  Glands.  —  In  its  course  the  lymph  passes 
through  many  kernel-like  masses,  the  lymphatic  glands. 
They  may  be  felt  in  the  armpits,  in  the  groins,  and  some- 
times in  the  neck.  Lymph  contains  corpuscles  which  are 
considered  the  same  as  the  colorless  blood  corpuscles.  It 


The  Blood  and  the  Lymph. 


79 


a— 1 


is  thought  that  these  corpuscles  are  formed  in  the  lymphatic 
glands.  In  a  disease  called  scrofula  the  lymphatic  glands 
become  swollen.  (See  Figs.  49  and  81.) 

The  Flow  of  Lymph.  —  The  flow  of  lymph  is  partly  due 
to  the  blood  pressure  in  the  capillaries,  this  pressure  is 
caused  by  the  heart.  In  our  bodies  the 
flow  of  lymph  is  largely  aided  by  any 
pressure  on  the  lymph  veins;  for,  on 
account  of  the  valves,  as  in  the  blood 
veins,  any  pressure  must  push  the  liquid 
toward  the  heart.  Thus  the  action  of 
the  muscles  in  the  limbs,  in  the  chest, 
in  the  abdomen,  in  the  movements  of 
breathing,  and  in  the  bending  of  the 
body,  etc.,  all  help  in  this  flow,  which  is 
always  very  much  slower  than  that  in 
the  blood  veins. 

Relations  of  Blood  Flow  and  Lymph 
Flow.  —  While  the  blood  leaves  the  left 
ventricle  by  one  tube,  the  aorta,  it  re- 
turns to  the  right  auricle,  not  merely 
by  the  two  caval  veins,  but  a  part  of 
the  blood  (i.e.  of  the  liquid  part  of  it) 
does  not  return  by  blood  veins,  but  hav- 
ing left  the  blood  system  proper  through 
the  thin  walls  of  the  capillaries,  is 
brought  back  by  the  lymph  veins,  which, 
however,  join  the  blood  veins  just  before 
they  empty  into  the  heart.  There  is 
only  one  set  of  distributing  tubes,  but  Flfubes  of  the  surface 
there  are  two  sets  of  collecting  or  re-  of,  thle  Arm-  LymPh 

Glands  at  a,  b,  c,  and  d 

turning  tubes. 


8o 


Physiology. 


The  Lymph.  —  Lymph  is   a  clear   liquid.     It   is   more 
watery  than  the  blood  plasma,  but  contains  a  share  of  all 


Left  Jugular  Vein 

Mouth  of 

Lymph  Vein . 

Left  Subcla- 
vian  Vein 


Right  Lymph  Vein 

Right  Subclavian 
Vein 


Pre-caval  Vein 


Post-caval  Vein 


Main  Lymph  Vein 
(Thoracic  Duct) 


Lymph  Capillaries 


-  Blood  Capillaries 


Fig.  50.    Diagram  of  the  Circulation  of  Blood  and  Lymph  (Back  View). 

its  nourishing  substances.  Lymph  may  be  defined  as 
" diluted  blood  minus  red  corpuscles"  The  blood  proper 
never  reaches  the  tissues. 


The  Blood  and  the  Lymph. 


81 


Lymph 


Capillary 


The  Cells  of  the  Body  live  in  Lymph.  —  The  cells  of  the 
tissues  are  bathed  in  the  lymph  which  fills  the  spaces  in 
the  connective  tissue  (and 
there  is  connective  tissue  in 
all  the  organs  of  the  body), 
as  water  may  fill  the  spaces 
left  between  stones  built  into 
a  wall.  The  cells  get.  all 
their  nourishment  from  the 
lymph,  and  into  the  lymph 
they  throw  all  their  waste 
matter. 


Oxygen 


Food 


Muscle 
Fiber 


Carbon 

Dioxid 


•Water 


Other 
Wastes 


Fig.  51.      Relation  of  Blood  and  Muscle. 
(Lymph  being  Middleman.) 


Importance  of  Lymph.  — 
We  can  see  that  the  move- 
ment and  renewal  of  lymph 
are  as  necessary  as  the  circu- 
lation of  the  blood  itself;  is, 
in  fact,  the  most  important 
part  of  it. 

Lymph  Cavities  or  Serous  Cavities.  —  We  have  noticed 
the  pericardial  liquid  (page  50).  There  is  also  a  small 
quantity  of  similar  liquid  around  the  lungs  in  the  pleural 
cavities,  and  in  the  abdominal  cavity,  around  the  digestive 
organs;  also  in  the  cavities  of  the  brain.  The  liquid  in 
each  case  is  lymph,  and  these  cavities,  often  called  serous 
cavities,  are  lymph  cavities.  They  communicate  with  the 
lymph  tubes. 

Dropsy.  —  In  health  the  amount  of  the  liquid  in  these 
cavities  is  small,  but  in  certain  disorders  it  may  accumu- 
late. In  general,  such  affections  are  called  "dropsy." 
The  lymph  may  also  accumulate  in  the  tissues  of  the 
extremities,  causing  swelling  of  the  limbs  called  "dropsy/5 


82  Physiology. 

Hypodermic  In jections.  —  When  it  is  desirable  that  a 
medicine  act  on  the  body  very  quickly,  it  is  sometimes 
introduced  under  the  skin.  This  is  done  by  means  of  a 
hypodermic  syringe,  which  is  a  syringe  with  a  slender, 
needle-shaped  nozzle.  By  means  of  this  the  medicine  is 
injected  into  the  tissues  under  the  skin.  Here  it  is  taken 
up  by  the  lymph  and  is  quickly  carried  through  the  system 
and  acts  on  the  cells  of  the  body.  If  the  same  medicine 
were  taken  into  the  stomach,  it  would  require  some  time 
for  it  to  be  absorbed  and  carried  into  the  tissues.  Hence 
time  is  gained.  We  can  see  how  much  advantage  there  is 
in  this  way  of  giving  medicine  when  the  physician  wishes 
to  stop  severe  pain. 

The  Spleen.  —  The  spleen  is  a  flattish  red  body  at  the 
left  end  of  the  stomach.  There  is  an  active  circulation  of 
blood  in  it,  and  it  is  supposed  to  form  the  colored  blood 
corpuscles.  It  is  often  called  a  blood  gland. 

Summary. —  i .  The  blood  consists  of  a  liquid,  the  plasma,  in  which 
float  the  colored  and  colorless  corpuscles. 

2.  The  color  of  blood  is  given  by  a  substance,  called  hemoglobin,  in 
the  colored  corpuscles. 

3.  When  blood    is   shed  it  coagulates,  tending  to  check  its  own 
escape. 

4.  Lymph  is  like  the  blood  diluted  and  lacking  the  colored  cor- 
puscles. 

5.  A  set  of  lymph  tubes  conveys  the  lymph  into  the  veins  to  join 
the  flow  toward  the  heart. 

6.  In  its  course  the  lymph  passes  through  the  lymphatic  glands. 

Questions.  —  i.    What  is  blood  poisoning  ? 

2.  Which  is  heavier,  blood  or  water  ? 

3.  Does  it  help  a  sick  person  to  bleed  him  ? 

4.  What  is  meant  by  good  blood  ?     Bad  blood  ? 

5.  What  is  meant  by  good  humored  ?     Bad  humored  ? 

6.  Does  the  blood  remain  the  same  from  day  to  day  ?    Or  even  from 
hour  to  hour  ? 


CHAPTER   IX. 
EXTERNAL  RESPIRATION. 

The  Close  Relation  between  Circulation  and  Respiration. 
—  Is  it  not  a  very  striking  fact  that  we  breathe  once  for 
every  four  heart  beats  ?  And  that  whatever  quickens  the 
breathing  also  quickens  the  heart  so  that  the  two  always 

keep  in  almost  the 
same  ratio?  Let  us 
try  to  learn  why  this 
is  so. 

The  Organs  of  Res- 
piration. —  i.     The 

lungs  and  air  tubes. 
2.  The  organs  which 
increase  and  dimin- 
ish the  size  of  the 
chest,  chief  among 
which  are  the  dia- 
phragm and  the  mus- 
cles acting  on  the 
ribs. 

External  Features 
of  the  Lungs.  — The  lungs  are  of  a  pinkish  color;  they  are 
very  elastic,  soft,  smooth,  and  moist. 

The  Air  Tubes.  —  The  windpipe,  or  trachea,  has  in  its 
walls  rings  of  gristle  or  cartilage,  which  keep  the  tube 
always  open.  These  rings  of  cartilage  are  not  complete 

83 


Fig.  52-    The  Trachea  and  Bronchial  Tubes,  showing 
Two  Clusters  of  Air  Sacs. 


Physiology, 


1.  Pulmonary  Orifice  3.    Left  Auriculo- Ventricular  Orifice 

2.  Aortic  Orifice-  4.    Right  Auriculo-Ventricular  Orifice 

The  heavy  black  line  between  the  heart  and  the  liver  represents  the  diaphragm. 

Fig.  53.     Front  View  of  the  Thorax.    The  Ribs  and  Breastbone  are  represented  in 
Relation  to  the  Lungs,  Heart,  and  other  Internal  Organs. 


External  Respiration.  85 

rings,  but  are  C-shaped.  As  the  windpipe  branches  (bron- 
chi) into  the  two  lungs,  the  cartilages  continue  in  the 
smaller  branches  which  extend  into  every  part  of  the  lungs. 

The  Internal  Structure  of  the  Lungs.  —  The  lungs  are 
full  of  small  cavities,  like  a  loaf  of  light  bread.  The  small 
cavities  are  called  air  sacs  or  air  vesicles,  and  each  air  sac 
communicates  with  the  end  of  one  of  the  branches  of  an 
air  tube,  through  which  air  comes  into  and  goes  out  of 
every  air  sac.  The  air  sacs  are  very  thin  walled,  and 
around  the  sacs  are  networks  of  the  fine  blood  tubes  called 
capillaries. 

Elastic  Tissue  in  the  Lungs.  —  The  air  sacs  and  air  tubes 
and  their  surrounding  blood  tubes  are  bound  together  by 
elastic  tissue,  which  fills  up  most  of  the  space  between  them. 

The  Mucous  Membrane.  —  The  lining  of  the  trachea  is 
a  mucous  membrane.     It  pours  out  on  its  surface  a  sub- 
stance     somewhat 
like  white  of  egg, 

M. l»j|   HKHji  'mm    called  mucus.  This 

N^ZJP  keeps  the  air  moist, 

and  catches  parti- 
cles of  dust  that  are 
in  the  inspired  air. 
Flg'54'  Cillaled  There  is  a  constant 

slow  current  of  mucus  toward  the  throat,  whence  it  is,  from 
time  to  time,  hawked  up. 

Ciiiums.  —  This  current  of  mucus  is  caused  by  the  ciii- 
ums projecting  from  the  lining  cells  of  the  trachea.  They 
are  little  hairlike  projections,  in  countless  numbers,  like  a 
field  of  grass,  each  cilium  having  the  power  of  bending 
back  and  forth,  making  a  quick  stroke  toward  the  throat, 
then  a  slower  recover  stroke.  Thus  the  united  wavelike 


86 


Physiology. 


action  of  the  myriads  of  lashing  ciliums  paddles  the  mucus 
headward. 

The  Pleura.  —  The  outside  of  each  lung  is  covered  by  a 
thin  membrane,  the  pleura,  which  completely  surrounds  it, 
except  at  the  root  of  the  lung,  where  the  bronchus  and 
blood  tubes  enter.  Here  the  pleura  turns  toward  and 
becomes  attached  to  the  inner  wall  of  the  chest,  forming 
its  lining  (still  called  the  pleura),  and  below  passes  over 

Trachea 


Pleural  Space  ,._ 
(Exaggerated) 


Chest  Wall 


Pleura 


Fig.  55.    Diagram  of  the  Lungs  and  Pleuras. 

the  upper  surface  of  the  diaphragm.  The  lung  is  thus 
free,  except  at  its  root,  where  the  air  and  blood  tubes 
enter.  A  very  small  quantity  of  liquid  moistens  the  sur- 
faces of  the  pleuras  on  the  outside  of  the  lung  and  the 
inside  of  the  chest  wall,  so  they  move  easily  one  upon  the 
other  during  respiration.  As  the  lungs  are  always  dis- 
tended enough  to  fill  the  chest  cavity,  these  two  surfaces 
are  always  in  contact. 

Pleurisy.  —  Pleurisy  is  an  inflammation  of  the  pleura. 
In  breathing  there  is  pain  from  friction  or  adhesion  of  the. 
pleuras  of  the  lungs  and  chest  wall. 


External   Respiration. 


Pneumonia.  —  Pneumonia  is  inflammation  of  the  lungs. 
It  was  formerly  called  ''lung  fever."  It  is  due  to  bacteria. 

The  Diaphragm.  —  The  diaphragm  is  a  thin  muscle  mak- 
ing a  complete  partition  between  the  abdominal  cavity  and 
the  chest  cavity.  It  is  convex  above  and  concave  below 
where  it  fits  over  the  liver  and  stomach.  Its  front  edge  is 
attached  to  the  inside  of  the  chest  wall  about  opposite  the 
lower  end  of  the  breastbone.  Its  general  position  is  shown 
in  Figs.  53,  55,  and  58. 

Triangularis  Sterni 
Internal  Mammary  Vessels 


Left  Phrenic 
Nerve 


Pleura 

Pulmonalis 

ura  Costalis 


Mediastinum  j  Sympathetic  Nerve 

Thoracic  Duct 


Vena  Azygos  Majo' 


Posterior 


<_  Thoracic  Duct  .  Pneumogastric  Nerves 

Fig.  56.    A  Cross-section  of  the  Chest,  showing  the  Heart.  Lungs,  and  Blood  Tubes. 

To  show  the  Action  of  the  Diaphragm  and  Lungs.  —  MATERIAL.  — 
Bell  jar  with  stopper,  sheet  of  rubber  (such  as  used  by  dentists)  large 


88  Physiology. 

enough  to  covel  the  mouth  of  the  jar,  toy  rubber  balloon,  cork  (rubber 
preferred),  glass  tube,  cotton  string,  collar  button. 

PREPARATION.  —  Lay  the  collar  button  on  the  center  of  the  sheet  of 
rubber,  double  the  rubber  over  it,  stretching  the  rubber  strongly  over 
the  head  of  the  button,  and  tie  the  head  firmly  in  its  place.  Stretch 
the  sheet  of  rubber  over  the  base  of  the  jar  with  the  base  of  the 
button  on  the  outside,  and  fasten  with  string.  Bore  a  hole  in  the  cork, 
and  fix  the  glass  tube  snugly  in  it,  so  that  the  lower  end  of  the  tube 
will  extend  about  half-way  down  the  jar.  Tie  the  balloon  on  the  lower 
end  of  the  glass  tube. 


CILIA I  LBRONCHIAL  TUBE. 


\ 


Fig-  57.    Minute  Structure  of  the  Lungs,  showing  Air  Sacs  and  Capillaries. 

EXPERIMENT  i.  —  Insert  the  balloon  and  tube  into  the  jar,  inflate 
the  balloon,  and  while  it  is  inflated  tightly  cork  the  jar.  If  all  the  parts 
fit  well,  the  balloon  should  now  remain  inflated,  and  the  rubber  which 
represents  the  diaphragm  will  be  arched  upward. 

EXPERIMENT  2.  —  Pull  the  diaphragm  down,  using  the  base  of  the 
collar  button  as  a  handle.  This  shows  the  expansion  of  the  lung  by 
the  pressure  of  the  external  air  when  more  space  is  given  by  the 
depression  of  the  diaphragm.  On  releasing  the  diaphragm,  it  springs 
upward,  and  the  balloon  becomes  smaller,  driving  out  part  of  the  air 
that  was  in  it.  This  shows  how  expiration  is  accomplished,  so  far  as 
the  diaphragm  is  concerned. 

If  a  bell  jar  is  not  at  hand,  a  lamp  chimney  or  a  quart  bottle  may  be 
used,  after  cutting  off  the  bottom,  as  follows :  File  a  deep  notch  across 


External  Respiration. 


89 


near  the  bottom ;  heat  an  iron  rod,  and  apply  the  end  of  it  to  one  end 
of  the  notch,  and  slowly  draw  the  rod  around  to  the  other  end  of  the 
notch  (the  rod  may  need  to  be  reheated).  After  cracking  off  the 
bottom  of  the  jar,  file  the  edges  so  they  will  not  cut  the  rubber. 

Let  each  pupil  make  a  drawing,  showing  the  position  of  the  parts  in 
inspiration  and  in  expiration. 

The  Movements  of  Respiration.  —  The  process  of  res- 
piration consists  of  two  acts,  inspiration  and  expiration. 


. . . .  Increased  Air 
Space 


Inspiration  Expiration 

Fig.  58-    Sections  of  the  Body  in  Inspiration  and  Expiration. 

Two  Active  Forces  in  Inspiration.  —  In  inspiration  the 
principal  active  forces  in  the  body  are,  first,  the  dia- 
phragm ;  and,  second,  the  muscles  which  raise  the  ribs. 

Work  of  the  Diaphragm  in  Inspiration.  —  The  diaphragm 
is  a  muscle,  and  when  its  fibers  shorten,  the  diaphragm  is 
pulled  down.  In  moving  down  it  presses  on  the  abdomi- 
nal organs,  and  makes  the  abdomen  protrude  forward  and 
sideways.  This  lowering  of  the  diaphragm  increases  the 
7— PHY 


90  Physiology,, 

space  in  the  chest.  Air,  from  the  outside,  enters  through 
the  trachea,  presses  on  the  inside  of  the  elastic  lungs,  and 
makes  their  bases  extend,  following  the  diaphragm  in  its 
descent.  The  bases  of  the  lungs  remain  in  contact  with 
the  upper  surface  of  the  diaphragm  all  the  time. 

Work  of  the  Chest  Walls  in  •  Inspiration.  —  Certain 
muscles  of  the  chest  wall  raise  the  ribs  and  breastbone. 
This  widens  the  chest,  and  the  air,  as  before,  presses  in 
through  the  open  windpipe,  and  keeps. the  sides  of  the 
lungs  in  contact  with  the  inner  surfaces  of  the  chest  walls. 

Effort  required  in  Depressing  the  Diaphragm.  —  Inspira- 
tion requires  considerable  effort,  because  the  diaphragm 
in  its  descent  presses  upon  the  elastic  organs  of  the 
abdomen  (stomach,  liver,  etc.),  and  these  organs,  in  turn, 
are  pressed  against  the  elastic  walls  of  the  abdomen.  It  is 
somewhat  like  pressing  a  pillow  down  into  a  rubber  bag; 
the  pillow  springs  up  as  soon  as  the  pressure  is  stopped, 
because  of  its  own  elasticity  as  well  as  that  of  the  bag. 
Therefore,  as  soon  as  the  diaphragm  relaxes,  the  elastic 
walls  of  the  abdomen  retreat,  and  the  abdominal  organs 
rise  to  their  former  place. 

Effort  required  in  Raising  the  Ribs.  —  When  the  ribs  are 
elevated,  the  cartilages  which  connect  the  front  ends  of  the 
bony  parts 'of  the  ribs  with  the  breastbone  (see  Fig.  6)  are 
slightly  bent.  When  the  muscles  relax,  the  elasticity  of 
the  rib  cartilages  makes  the  ribs  spring  back  to  their 
former  position,  thus  reducing  the  chest  to  its  former 
width. 

Expiration  Easy.  —  Thus  we  see  why  expiration  is  easy; 
in  fact,  "does  itself"  (in  ordinary  respiration)  by  elastic 
reactions.  But  inspiration  is  harder  than  it  would  be  if  it 


External   Respiration.  9 1 

were  not  for  the  fact  that  the  descent  of  the  diaphragm 
meets  resistance,  and  the  ribs,  in  rising,  have  to  overcome 
resistance  in  bending  the  rib  cartilages,  and  in  raising  the 
weight  of  the  chest  walls  and  shoulders. 

Potential  Energy  stored  in  a  Door  Spring.  —  When  one 
opens  a  door  that  has  a  spring  to  shut  it,  he  has  to  use 
more  force  to  open  the  door  than  he  would  if  he  did  not 
have  to  bend  (twist  or  compress)  the  spring  at  the  same 
time.  But  no  effort  is  needed  to  shut  the  door.  The  door 
was  opened  and  shut  at  the  same  time ;  i.e.  when  the  door 
was  opened,  force  was  stored  in  the  spring  (in  the  form  of 
what  is  called  potential  energy),  and  this  stored  energy 
shuts  the  door  while  we  pass  on.  We  can  better  afford  to 
expend  more  energy  while  opening  the  door  than  to  take 
the  extra  time  to  shut  it.  If,  then,  a  door  with  such  spring 
were  fastened  open,  it  might  remain  open  for  a  long  time. 
When  released  it  flies  shut.  If  one,  in  this  case,  asks, 
"  Who  shut  the  door  ? "  the  answer  is,  "  The  person  who 
opened  it." 

The  Storing  of  Energy  during  Inspiration.  —  So  in  the 
act  of  inspiration  we  perform  a  double  work  in  storing 
energy  by  which  the  expiration  is  performed  without  active 
muscular  effort. 

Review  of  Forces  of  Respiration :  — 
Forces  of  Inspiration. 

1 .  Depression  of  the  diaphragm. 

2.  Muscles  elevating  the  ribs. 

3.  Pressure  of  the  external  air. 

Resistances  to . Inspiration . 

l .   Compression  of  the  abdominal  organs  and  stretching  abdominal 
walls. 


92  Physiology. 

2.  Bending  the  rib  cartilages  and  lifting  the  chest. 

3.  Stretching  the  lungs. 

Elastic  Reactions  of  Expiration. 

1 .  Elastic  reaction  of  the  abdominal  walls  and  contents, 

2.  Elastic  reaction  of  the  rib  cartilages. 

3.  Elastic  reaction  of  the  lungs. 

Forced  Respiration.  —  Thus  far  we  have  been  speaking 
of  ordinary  respiration.  In  forced  respiration,  as  in  shout- 
ing, many  muscles  are  brought  into  play  to  expel  the  air 
rapidly  and  forcibly.  In  such  an  act  as  coughing  there  is 
vigorous  action  of  the  abdominal  muscles. 

Abdominal  and  Thoracic  Respiration.  —  The  main  part  of 
respiration  is  performed  by  the  diaphragm,  and  is  there- 
fore called  diaphragmatic  or  abdominal  breathing.  Breath- 
ing by  means  of  the  chest  walls  is  called  thoracic,  or  costal 
breathing. 

The  Rate  of  Respiration.  —  Adults  breathe  about  seven- 
teen or  eighteen  times  a  minute,  or  about  one  breath  to 
four  heart  beats.  The  rate  is  increased  by  exercise,  tem- 
perature, digestion,  excitement,  age,  etc. 

Special  Forms  of  Breathing.  —  Coughing  is  a  forcible 
expiration,  usually  directed  through  the  mouth,  and  for  the 
purpose  of  getting  rid  of  some  irritating  substance.  In 
sneezing  there  is  first  a  deep  inspiration,  and  then  the  air 
is  forced  out,  chiefly  through  the  nose.  Sneezing  may  be 
prevented  by  pressing  firmly  on  the  upper  lip.  Hiccuping 
is  sudden  inspiration,  produced  by  a  jerky  action  of  the 
diaphragm,  accompanied  by  a  sudden  closing  of  the  en- 
trance to  the  windpipe.  In  case  of  choking  it  is  well  to 
hold  the  head  well  forward,  and  perhaps  downward.  A 
smart  slap  between  the  shoulders  sometimes  helps  dislodge 


External  Respiration.  93 

anything  stuck  in  the  throat,  and  it  may  be  necessary  to 
hold  a  child  with  the  head  downward.     There  are  various 


5 


* 


tl 


COMPLEMENTAL    AIR. 

120   CUBIC   INCHES. 
AIR   THAT  CAN  BE  BUT  SELDOM   IS   TAKEN   IN. 


TIDAL    AIR.— 20   to   30    Cubic   Inches   Air    Taken   in 
and   Sent   out   at    Each    Breath. 


RESERVE  AIR. 

100   CUBIC   INCHES. 
AIR   THAT  CAN   BE   BUT  IS   SELDOM   DRIVEN   OUT. 


RESIDUAL  AIR. 

100   CUBIC   INCHES. 
AIR   THAT  CANNOT  BE   DRIVEN   OUT. 


Fig.  59.    Diagram  of  Lung  Capacity. 


I 


s. 
o 


other  peculiar  forms  of  respiration,  such  as  yawning,  sniff- 
ing, laughing,  etc.,  which  you  can  explain  after  watching 
and  thinking  about  them. 


94  Physiology. 

Capacity  of  the  Lungs.  —  Have  the  class  stand,  and  each 
pupil  raise  his  right  hand. 

1 .  Tidal  Air.  —  Let  all  breathe  together,  at  the  ordinary  rate  and 
depth,  and  let  the  hand  rise  about  three  inches  during  inspiration,  and 
fall  again  during  expiration.    The  amount  of  air  taken  in  at  an  ordinary 
breath  is  from  20  to  30  cubic  inches,  or  about  a  pint.     This  is  called 
tidal  air. 

2.  Complemental  Air. — As  before,  let  the  hand  go  up  and  down 
with  the  breathing,  but  at  the  end  of  the  third  inspiration,  instead  of 
stopping  with  the  usual  amount,  keep  on  breathing  in  as  much  as  pos- 
sible, letting  the  hand  rise  accordingly.     This  air  that  can  be  taken  in 
above  the  ordinary  breath   is   called  the  complemental  air,  and  it  is 
estimated  to  be,  on  the  average,  about  120  cubic  inches. 

3.  Reserve  Air.  —  Begin  as  before,  and  at  what  would  be  the  end 
of  the  third  expiration  continue  to  drive  out  as  much  air  as  possible, 
indicating  the  degree    by  lowering  the  hand.     This  air  that  can  be 
breathed  out  beyond  the  ordinary  expiration  is  called  the  reserve  air, 
and  is  reckoned  at  about  100  cubic  inches. 

4.  Residual  Air.  —  The  air  cannot  all  be  breathed  out.     The  re- 
mainder is  called  the  residual  air,  and  is  computed  to  be  about  100 
cubic  inches. 

The  Vital  Capacity.  —  All  the  air  that  can  be  breathed  out  after  a 
full  inspiration,  i.e.  the  sum  of  the  complemental,  tidal,  and  reserve 
air,  would  be  about  240  to  250  cubic  inches,  and  is  called  the  vital 
capacity.  Of  course  these  figures  represent  only  the  average  of  cer- 
tain experiments  and  observations.  By  practice  any  one  can  consid- 
erably increase  his  vital  capacity. 

A  Test  of  the  Capacity  of  the  Lungs.  —  A  simple  method  of  measur- 
ing these  stages  of  respiratidn  is  to  take  a  gallon  bottle  and  first  care- 
' fully  graduate  it  to  pints  by  pouring  in  water  and  marking  on  the 
outside  with  a  file.  Then  fill  the  bottle  with  water,  invert  it  in  a  trough 
of  water,  and  exhale  into  it  by  means  of  a  rubber  tube. 

Hygiene  of  Breathing. — Those  persons  who  take  con- 
stant exercise  in  the  open  air  are  not  likely  to  suffer  much 
from  deficient  respiration.  But  persons  who  lead  an  indoor 


External   Respiration.  95 

life,  especially  those  who  are  sitting  much  of  the  time,  need 
to  pay  especial  attention  to  the  matter. 

The  Nasal  Passages.  —  The  nasal  passages  are  fitted  for 
the  introduction  of  the  air  (i)  by  being  narrow,  but  of 
large  area;  (2)  by  having  their  lining  membranes  richly 
supplied  with  blood ;  (3)  by  the  abundant  secretion  of 
mucus  by  this  membrane.  The  air,  coming  through  this 
narrow  channel,  is  warmed,  and  a  large  part  of  any  dust 
it  may  contain  is  caught  by  the  sticky  mucus  that  covers 
all  the  walls  of  this  passage-way. 

Adenoids.  —  When  any  person  breathes  through  the 
mouth,  there  is  something  wrong  somewhere  in  the  nasal 
passages.  Children  who  breathe  through  the  mouth  and 
"  snore "  at  night  generally  have  a  growth  of  gland-like 
tissue  called  "  adenoids  "  at  the  back  part  of  the  nose  and 
behind  the  palate.  Not  only  is  breathing  through  the 
mouth  bad  because  it  allows  cold  air  and  dust  to  go  down 
into  the  windpipe,  but  the  mouth  breather  cannot  get 
enough  air  properly  to  aerate  his  blood.  Mouth-breathing 
children,  therefore,  are  frequently  peevish  and  not  dis- 
posed to  play.  They  do  not  sleep  or  eat  well,  are  apt  to 
be  croupy,  and  are  more  liable  than  nose-breathing  chil- 
dren to  contract  diseases  like  diphtheria  and  croup.  Such 
children  should  be  taken  to  the  doctor  and  the  adenoids 
should  be  removed. 

Deep  Breathing.  —  It  is  a  grateful  relief  to  the  whole 
system  to  stand,  stretch,  inhale  deeply  and  slowly  several 
times,  and  to  repeat  this  every  hour  or  so.  Every  one 
engaged  in  office  work  or  studying  should  form  this  habit, 
especially  if  he  does  not  give  an  hour  daily  to  exercise. 

Control  of  Respiration.  —  Breathing  is  an  involuntary 
action.  It  is  under  the  control  of  the  nervous  system,  and, 


96  Physiology. 

without  attention  on  our  part,  it  goes  on,  varying  in  rate 
according  to  the  needs  of  the  body.  About  every  fifth 
breath  is  a  little  deeper  than  the  others,  and  if  we  are  sit- 
ting in  a  cramped  position,  or  are  depressed,  this  occasional 
deeper  breath  is  still  more  marked  and  is  called  a  sigh. 
If  the  tissues  are  not  well  supplied  with  oxygen,  they  make 
it  known  to  nerve  centers  through  the  nerves,  and,  by 
reflex  action,  breathing  is  quickened. 

Summary.  —  I.  In  the  lungs  the  air  and  blood  are  brought  very  close 
together,  only  the  wall  of  the  capillary  and  that  of  the  air  vesicle  being 
between  them. 

2.  Through  these  two  layers  oxygen  passes  from  the  air  sac  into  the 
blood.     Carbon  dioxid,  water  vapor,  and  other  wastes  pass  from  the 
blood  into  the  air  sac. 

3.  The  mucous  membrane  of  the  air  passages  secretes  mucus  which 
is  driven  toward  the  nostrils  by  the  ciliums. 

4.  The  chest  is  lengthened  by  the  lowering  of  the  diaphragm,  and 
widened  by  the  lifting  of  the  ribs,  giving  greater  space,  which  is  filled 
by  external  air  expanding  the  lungs. 

5.  Inspiration  requires  extra  effort ;  but  ordinary  expiration  is  with- 
out effort  because  of  the  elastic  reactions. 

6.  Forced  expiration,  as  coughing,  requires  active  muscular  effort. 

7.  The  vital  capacity  may  be  increased  by  practice  and  by  exercise. 

8.  We  should  breathe  through  the  nose,  not  through  the  mouth. 

9.  Respiration  is  under  the  control  of  the  nervous  system. 

Questions.  —  i.  Is  5t  well  to  see  how  long  one  can  hold  his  breath  ? 

2.  Should  the  head  be  covered  by  bedclothes  ? 

3.  How  is  respiration  affected  by  a  stooping  posture  ? 

4.  What  are  the  "lights"  of  an  animal  ? 

5.  Of  what  advantage  is  it  that  the  cartilages  of  the  windpipe  are 
C-shaped,  and  not  complete  rings  ? 

6.  From  the  statements  in  this  chapter  of  the  amount  of  air  taken  in 
at  each  breath  and  of  the  rate  of  breathing,  find  out  how  much  air  is 
breathed  in  an  hour.     How  much  in  twenty-four  hours  ? 


CHAPTER   X. 
INTERNAL  RESPIRATION. 

Composition  of  the  Air.  —  Air  has  about  20  per  cent  oxy- 
gen and  80  per  cent  nitrogen,  or  one  fifth  oxygen  and  four 
fifths  nitrogen.  There  'is  a  very  small  amount  of  carbon 
dioxid,  .and  usually  there  are  traces  of  other  gases. 

Experiments  illustrating  Internal  Respiration.  —  MATERIAL  NECES- 
SARY. —  A  piece  of  candle  an  inch  or  two  long,  two  tumblers,  a  tube 
eight  inches  long  (a  straw  will  serve),  a  nail,  and  lime  water.  The  lime 
water  should  be  prepared  the  day  before  by  putting  a  piece  of  fresh 
quicklime  as  big  as  a  hen's  egg  in  a  quart  of  water.  The  next  morning 
carefully  pour  off  the  clear  water  for  use  in  experiment. 

EXPERIMENT  i.  —  Light  the  candle  and  hold  a  cold  tumbler  inverted 
a  little  above  it.  The  moisture  that  dims  the  inside  of  the  tumbler  is 
water  that  has  been  produced  by  the  burning  of  the  candle.  The  oxy- 
gen of  the  air  unites  with  something  in  the  candle  and  forms  water. 

EXPERIMENT  2.  —  Breathe  into  a  cold  tumbler.  The  tumbler  is 
dimmed  by  the  water  in  the  air  we  breathe  out. 

EXPERIMENT  3.  —  Lower  a  tumbler  over  the  burning  candle  till  the 
tumbler  rests  on  the  table.  Observe  that  the  flame  is  soon  put  out. 
Carefully  lift  the  tumbler  and  slip  one  hand  under  it  so  that  the  palm 
tightly  covers  the  mouth  of  the  tumbler.  Invert  the  tumbler.  Lift  one 
edge  of  the  hand  and  pour  in  about  two  tablespoonfuls  of  lime  water. 
Thoroughly  shake  the  tumbler,  keeping  it  tightly  closed.  The  lime 
water  is  turned  milky  by  the  carbon  dioxid  produced  by  the  burning 
candle.  There  is  carbon  in  the  material  of  the  candle,  and  the  union  of 
oxygen  with  this  carbon  produces  carbon  dioxid. 

EXPERIMENT  4.  —  Pour  about  two  tablespoonfuls  of  lime  water  into 
a  tumbler  and  breathe  through  it  by  means  of  a  tube.  The  lime  water 
is  turned  milky  by  the  carbon  dioxid  in  the  breath.  There  is  carbon  in 

97 


98  Physiology, 

the  tissues  of  the  body.  Oxygen  unites  with  this  carbon,  forming  car- 
bon dioxid.  We  know  that  there  is  carbon  in  beef,  for  when  it  is  over- 
baked  we  see  the  black  carbon  where  it  is  charred.  There  is  carbon  in 
our  muscles  and  in  all  the  other  tissues. 

EXPERIMENT  5. —  Place  a  nail,  or  any  piece  of  iron,  in  a  tumbler  of 
water.  It  will  soon  rust.  Rusting  is  caused  by  the  union  of  oxygen 
with  the  iron.  When  anything  unites  with  oxygen  it  is  said  to  oxidize. 
When  the  union  is  rapid,  as  with  the  burning  candle,  it  is  called  com- 
bustion. 

EXPERIMENT  6.  —  Hold  a  thermometer  at  arm's  length.  It  shows 
the  temperature  of  the  air,  —  of  the  air  you  are  breathing  in.  Breathe 
for  a  few  minutes  upon  the  bulb  of  the  thermometer  and  you  have  proof 
that  the  air  we  breathe  out  is  warmer  than  the  air  we  breathe  in. 

How  the  Body  is  like  a  Candle.  —  The  burning  candle 
and  the  body  both  produce  heat.  To  do  this  each  must 
have  oxygen.  The  oxygen  unites  with  carbon  and  other 
elements  in  each,  and  produces  carbon  dioxid,  water,  and 
.other  substances.  And  just  as  a  candle  flame  is  soon  put 
out  in  a  closed  tumbler,  so  life  would  be  destroyed  by  suf- 
focation if  an  animal  were  shut  in  an  air-tight  room. 

Exchanges  between  the  Air  and  the  Blood  in  the  Lungs.  — 

Whatever  the  air  coming  from  the  lungs  contains  that  was 
not  in  the  air  entering  them  it  has  taken  from  the  blood, 
and  what  the  air  has  lost  it  has  given  to  the  blood.  The 
air  in  the  air  vesicle  is  separated  from  the  blood  in  the 
pulmonary  capillaries  only  by  the  thin  wall  of  the  air  vesicle 
and  the  thin  capillary  wall. 

What  the  Air  gets  from  the  Blood. — Carbon  dioxid,  water, 
and  other  waste  matters  pass  from  the  blood  through  this 
thin  partition  into  the  air  vesicle,  to  be  sent  out  by  later 
expiration  through  the  bronchial  tubes  and  windpipe.  The 
air  also  gets  heat  from  the  blood  (see  Fig.  60). 


Internal   Respiration. 


99 


What  the  Blood  gets  from  the  Air.  —  Oxygen  from  the  air 
in  the  vesicle  passes  through  these  layers  into  the  plasma, 
and  most  of  it  is  quickly  picked  up  by  the  colored  corpus- 
cles. The  colored  corpuscles  are  the  carriers  of  oxygen. 


BRONCHIAL  TUBE 


FROM  PULMONARY  ARTERY 


TO  PULMONARY  VEIN 


Fig.  60.    Exchanges  between  the  Air  and  the  Blood  in  the  Lungs. 

Hemoglobin  and  Oxy-hemoglobin.  —  The  hemoglobin  in 
the  colored  corpuscles  is  eager  to  unite  with  oxygen. 
Hemoglobin  is  of  a  dark  color,  and  gives  the  dark  color 
to  the  blood  which  enters  the  lungs.  When  oxygen  unites 
with  the  hemoglobin  it  forms  oxy-hemoglobin,  which  is  of  a 
bright  red  color.  Hence  the  change  in  the  color  of  the  blood 


100 


Physiology. 


in  the  lungs  from  a  dark  bluish  red  to  a  bright  scarlet 
This  bright  blood  is  usually  called  "  arterial,"  and  the  dark 
"venous";  but  it  must  be  remembered  that  the  blood  in 
the  pulmonary  artery  is  dark,  and  in  the  pulmonary  veins 
bright. 

"V 

v\ 


Fig.  61.    Circulation  in  the  Capillaries  of  the  Lungs  and  in  the  Capillaries  of  the  Body. 

The  Changes  in  the  Blood.  —  What  does  the  blood  do 
with  the  oxygen  that  it  gets  in  the  lungs,  and  where  did  it 
get  the  carbon  dioxid  and  other  impurities  that  it  brings  to 
the  lungs  ?  Let  us  follow  the  blood  and  see.  From  the 
pulmonary  veins  the  blood  goes  to  the  left  heart,  and  is 
pumped  to  all  the  tissues  except  the  lungs.  Let  us  follow 
a  branch  of  the  aorta  that  leads  to  a  muscle. 

The  Production  of  Heat  and  Motion  in  the  Body.  —  When 
a  muscle  works  it  becomes  warmer.  The  rise  in  tempera- 
ture has  been  repeatedly  proved  by  experiment.  We  know 
that  the  blood  is  flowing  more  rapidly  through  the  muscle 


Internal   Respiration^. 


when  it  is  at  work.  The  more  rapid  stream  brings  the 
muscle  more  oxygen.  This  it  needs,  for  it  is  by  the  oxida- 
tion of  the  muscle  (or  substance  in  it)  that  the  muscle 
produces  heat  and  motion.  The  oxidation  in  our  tissues  is 
a  slow  oxidation,  more  like  the  rusting  of  iron  than  the 
burning  of  a  candle.  Oxidation  in  our  bodies  never  pro- 
duces a  high  degree  of  heat  and  never  produces  light. 

Increased  Blood  Flow  is  the  Result  of  Exercise.  —  When 
we  exercise,  the  muscles  need  more  oxygen.  They  also 
need  to  have  removed  the  waste  matters  that  they  are  so 
rapidly  producing  at  this  time.  How  is  the  oxygen  brought 
and  the  waste  removed  ?  By  the  blood,  you  answer.  True ; 
but  what  makes  the  blood  come  and  go  faster  at  this  time  ? 
By  reflex  action,  you  reply.  The  muscles  send  a  message 
to  a  nerve  center,  and  this  nerve  center  sends  back  a  mes- 
sage to  the  blood  tubes,  making  them  widen,  and  the  heart 
also  may  be  made  to  beat  faster. 

Increased  Respiration  from  Exercise.  —  But  would  it  do 
any  good  to  have  the  blood  flow  through  the  muscles  faster, 
if  it  could  not  bring  more  oxygen,  and  take  away  and  get 
rid  of  more  wastes  ?  You  will  say  no.  To  give  the  extra 
oxygen  and  take  out  the  carbon  dioxid,  the  lungs  cannot, 
of  themselves,  take  in  and  send  out  air.  The  work  of 
pumping  air  depends  on  the  muscles  of  respiration,  the 
diaphragm,  and  the  muscles  that  elevate  the  ribs.  These 
muscles  will  not  work  faster  unless  they  are  ordered  to  do 
so.  A  message  must  be  sent  to  them  telling  of  the  need. 
Thus,  by  a  series  of  reflex  actions,  all  these  processes  are 
kept  in  close  relation  to  each  other.  It  must  be  borne  in 
mind  that  increased  blood  flow  is  the  result,  and  not  the 
cause,  of  the  increased  activity  of  the  tissues. 

Temperature  of  the  Body.  —  Insert  the  bulb  of  a  thermometer  into 
the  mouth,  and  keep  it  there  three  or  four  minutes  to  find  the  tempera- 


IQ2^  physiology. 

ture  of  the  inside  of  the  body.  For  this  it  is  better  to  use  a  clinical 
thermometer,  if  one  can  be  obtained.  The  average  temperature  of  the 
tissues  within  the  body  is  about  98.5°  F. 

How  the  Body  is  like  a  Stove.  —  The  body  may  be  com- 
pared to  a  stove.  Into  one  we  put  fuel  and  produce  heat. 
In  the  other  we  get  heat  from  food.  Both  take  in  oxygen. 
Both  produce  carbon  dioxid,  water,  and  other  waste  matter. 

How  the  Body  differs  from  a  Stove.  —  But  the  body  is  not 
like  the  stove  in  burning  the  fuel  (food)  directly.  The 
food  is  first  made  into  tissues,  or  material  stored  in  the 
tissues.  It  is  as  though  we  were  to  build  a  stove  entirely 
of  coal,  and  then  start  a  fire  in  it.  In  that  case  it  would 
produce  heat  not  merely  by  burning  in  one  place  within, 
but  would  be  burning  throughout  the  whole  of  its  sub- 
stance. This  is  the  case  with  the  body. 

Oxidation  in  Tissue  the  Source  of  Heat  in  the  Body.  — 

The  muscles  make  up  nearly  half  of  the  weight  of  the 
body.  They  are  more  active  than  most  of  the  tissues. 
We  would  naturally  infer,  as  is  the  fact,  that  they  are  the 
chief  source  of  the  heat  produced  in  our  bodies.  The 
tissues  of  the  body  are  oxidizing  all  the  time.  But  when 
in  vigorous  action  they  oxidize  very  much  more  rapidly. 

Production  of  Heat  in  the  Liver.  —  Next  to  the  muscles, 
in  importance  as  a  heat  producer,  is  the  liver,  which  is  the 
largest  gland  in  the  body,  and,  as  we  shall  soon  see,  one  of 
the  most  active.  The  blood,  as  it  leaves  the  liver  by  the 
hepatic  vein,  is  hotter  than  anywhere  else  in  the  body. 

How  the  Body  is  like  a  Locomotive.  —  But  it  will  be  better 
to  compare  the  body  to  a  locomotive,  as  we  produce  not 
only  heat,  but  motion: — I.  Both  are  warm;  2.  Both 
move;  3.  Both  use  fuel  (food  or  coal);  4.  Both  take  in 


Internal  Respiration.  103 

air.     5.    Both  give  off  gases,  consisting  mainly  of  carbon 
dioxid  and  water  vapor. 

How  the  Body  differs  from  a  Locomotive  :  —  i.  The  body 
does  not  get  hot  enough  to  burn;  i.e.  the  oxidation  is 
relatively  slow,  and  is  not  combustion.  2.  The  oxidation 
of  the  body  never  produces  light.  3.  The  oxidation  in  the 
body  is  always  in  the  presence  of  moisture. 

The  Amount  of  Carbon  Dioxid  given  off. — When  the 
breath  is  held  for  some  time,  the  carbon  dioxid  in  the 
expired  air  may  reach  7  or  8  per  cent.  During  violent 
exercise  the  amount  of  carbon  dioxid  given  off  may  be 
more  than  twice  as  much  as  when  we  are  at  rest.  In 
ordinary  respiration  there  is  one  hundred  times  as  much 
carbon  dioxid  in  the  air  we  breathe  out  as  there  was  when 
it  was  taken  in.  Oxygen  is  carried  chiefly  in  the  cor- 
puscles, but  the  carbon  dioxid  is  carried  in  both  plasma 
and  corpuscles. 

Effect  of  Re-breathing  Air.  —  Every  one  knows  how 
unpleasant  it  is  to  breathe  the  air  of  a  close  room  where 
many  people  are  present.  In  many  persons  such  air 
causes  headache  and  drowsiness.  This  effect  is  not  due 
to  the  reduced  amount  of  oxygen,  nor  is  it  due  to  the 
increase  of  carbon  dioxid.  It  is  believed  to  be  due  to 
the  "  organic  impurities "  which  are  thrown  out  in  the 
expired  breath.  It  is  this  matter  that  gives  the  offensive 
odor  to  a  room  which  is  kept  close  and  warm  after  a  crowd 
has  been  in  it.  If  in  a  crowded  lecture  room  you  divide 
the  space  by  the  number  of  people  present,  you  find  that 
each  one  has  really  very  little  room.  In  such  rooms 
special  attention  to  ventilation  is  necessary,  or  great  injury 
will  be  done.  When  we  learn  how  many  cases  of  lung 


1 04  Physiology. 

diseases  are  found  wherever  people  are  crowded  into  ill- 
ventilated  rooms,  we  can  realize  the  force  of  the  statement, 
"  Man's  own  breath  is  his  worst  enemy." 

Summary  of  Respiration. — The  tissues  need  oxygen; 
air  is  pumped  into  the  lungs ;  this  air  gives  oxygen  to  the 
blood ;  the  blood  carries  it  to  the  tissues. 

In  oxidizing,  the  tissues  produce  energy  (heat  and 
motion)  and  give  off  waste  matter  (water,  carbon  dioxid, 
etc.);  these  the  blood  carries  to  the  lungs,  the  lungs  give 
them  to  the  air,  and  the  air  carries  them  out  of  the  body. 

The  pumping  of  the  air  in  and  out  and  the  exchanges 
between  the  air  and  the  blood  in  the  lungs  may  be  called 
"external,  or  mechanical  respiration."  The  action  of  the 
oxygen  of  the  blood  in  the  tissues  is  the  "  real,  or  internal 
respiration." 

Summary.  —  i.  In  passing  through  the  lungs  air  loses  oxygen,  and 
gains  water,  carbon  dioxid,  and  other  wastes. 

2.  Oxygen  is  carried  chiefly  by  the  colored  corpuscles  of  the  blood; 
it  unites  with  hemoglobin  in  the  corpuscles,  forming  oxyhemoglobin, 
and  gives  the  blood  its  bright  scarlet  color. 

3.  The  energy  of  heat  and  motion   in  the  body  results  from  the 
oxidations  in  the  tissues. 

4.  Air  once  breathed  is  unwholesome.     The  air  of  living  and  sleep- 
ing rooms  needs  constant  renewal. 

5.  When  we  exercise  more,  the  muscles  need  more  oxygen,  so  the 
heart  must  beat  faster  and  we  must  breathe  faster. 

6.  The  body  is  like  a  locomotive  in  producing  heat  and  motion  by 
oxidation. 

7.  Air,  once  breathed,  has    one   hundred   times   as   much   carbon 
dioxid  as  before. 

Questions.  — i.  In  what  part  of  the  lungs  is  the  best  air?  Where 
the  worst? 

2.  Is  it  easy  to  determine  by  the  color  of  blood  flowing  from  a 
wound  whether  it  is  arterial  or  venous?  Why? 


Internal  Respiration.  105 

3.  How  is  the  air  of  a  room  affected  by  having  many  lamps  or  gas 
jets  burning  ? 

4.  How  is  air  affected  by  gasolene  or  kerosene  stoves  ? 

5.  Could  a  locomotive  be  run  by  feeding  it  with  bread  and  meat  ? 


8 — PHY 


CHAPTER  XT. 
VENTILATION  AND  HEATING. 

Need  of  Proper  Ventilation.  —  When  one  is  actively 
exercising  he  may  keep  warm  outdoors  even  on  a  cold 
winter  day.  For  the  heat  of  the  body  depends  on  its 
internal  fires,  the  oxidation  of  its  tissues.  But  if  we  are 
inactive,  these  fires  burn  feebly,  and  we  need  outside  heat. 
While  air  is  free,  it  really  costs  a  good  deal  of  money  to 
have  it  properly  warmed. 

A  Lack  of  Effective  Systems  of  Ventilation.  —  Lung 
diseases  are  rare  in  the  regions  where  the  windows  and 
doors  may  be  kept  open  most  of  the  days  of  the  year.  It 
is  from  shutting  ourselves  in  so  closely  that  we  suffer. 
This  is  especially  true  where  many  people  are  housed  in  a 
comparatively  small  space,  as  in  many  public  buildings. 
But  in  our  private  dwellings,  even  when  the  owners  are 
amply  able  to  secure  the  best  appliances,  defective  appa- 
ratus is  often  put  in.  Any  system  that  does  not  provide  for 
a  constant  reneival  of  the  air  is  defective. 

The  General  Principles  of  Ventilation.  —  Of  the  forces 
that  renew  the  air  of  rooms  two  are  natural,  (i)  diffusion 
and  (2)  the  wind  ;  and  two  are  artificial,  (3)  warm  air  shafts 
and  (4)  fan  systems. 

Diffusion.  —  Gases  tend  to  mix.  We  know  that  if  a 
bottle  containing  an  odorous  substance  is  opened  in  a 
room  where  there  are  no  air  currents  the  odor  tends  to 

106 


Ventilation  and  Heating.  107 

spread  equally  through  the  room.  If  a  person  is  in  one 
corner  of  a  large  room,  where  there  are  no  inlets  or  out- 
lets, and  no  currents,  as  he  uses  the  oxygen  immediately 
around  him,  the  oxygen  farther  away  will  diffuse  toward 
him  so  that  he  will  continue  to  get  oxygen  as  long  as  there 
is  any  in  the  room.  So,  too,  the  gases  that  he  breathes 
out  will  not  remain  confined  to  the  space  directly  about 
him,  but  will  spread  nearly  evenly  throughout  the  room. 
The  same  takes  place  in  the  open  air,  without  wind.  So, 
then,  if  the  windows  and  doors  are  open,  the  air  of  the 
room  will  be  renewed  by  diffusion. 

Wind.  —  Motion  of  the  air  renews  faster  than  mere  dif- 
fusion. Strong  wind  forces  its  way  through  the  cracks 
around  windows,  and  when  windows  are  open  on  opposite 
sides  of  a  room  there  is  usually  enough  breeze  to  renew 
the  air.  But  during  part  of  the  year  this  cannot  be  done. 

Artificial  Renewal  of  the  Air.  —  The  renewal  of  the  air 
in  most  cases  depends  on  the  fact  that  heated  air  rises. 
Heat  expands  air.  It  is  then  lighter,  bulk  for  bulk,  than 
cooler  air.  The  heavier  surrounding  air  presses  the  lighter 
air  upward.  If  there  are  outlets  above  and  below,  the 
heavier,  colder  air  will  press  in  below,  and  push  the  lighter, 
warmer  air  out  above. 

Grates  as  Heaters.  —  Grates  are  the  simplest  and  prob- 
ably the  earliest  form  of  heater.  The  fire  throws  out  heat 
in  straight  lines,  or  as  we  say,  radiates  heat  into  the  room. 
So  much  of  the  heat  goes  directly  up  the  chimney  that  a 
grate  is  very  wasteful  of  fuel. 

Grates  as  Ventilators.  —  But  a  grate  is  an  excellent  ven- 
tilator. There  is  always  a  decided  draft  toward  a  grate 
fire.  This  means  a  constant  renewal  of  air.  The  air 


io8  Physiology. 

pushing  toward  the  grate  may  be  cold,  and  this  has  disad- 
vantages that  are  hard  to  overcome  in  cold  weather  if  there 
is  no  other  way  of  supplying  heat.  But  it  is  a  serious 
question  whether,  with  all  our  modern  improvements  in 
heating,  we  have  better  air  in  our  houses,  or  take  cold  less 
often  than  our  grandfathers,  even  if  they  did  "roast  on 
one  side  while  they  froze  on  the  other." 

Stoves  as  Heaters.  —  A  stove  is  a  very  much  more  effec- 
tive heater  than  a  grate.  In  the  first  place  the  stove  gives 
off  heat  on  all  sides.  In  the  second  place  a  good  deal  of 
heat  is  given  off  by  the  stovepipe ;  while  in  the  grate 
almost  no  heat  is  saved  from  the  flame  and  smoke. 
Again,  the  fire  can  be  better  regulated  in  the  stove. 

Air  Currents  produced  by  Stoves.  —  There  is  always  a 
current  of  heated  air  rising  above  a  hot  stove.  Children 
make  whirligigs  and  other  toys  to  place  in  these  up-currents. 
When  this  heated  air  reaches  the  ceiling  it  passes  along 
the  ceiling,  and  comes  down  along  the  walls  in  the  colder 
parts  of  the  room.  At  the  same  time  colder  air  is  flowing 
along  the  floor  toward  the  stove.  This,  in  turn,  is  heated 
and  rises,  making  a  constant  circuit,  along  the  floor  to  the 
stove,  up  from  the  stove  to  the  ceiling,  along  the  ceiling 
to  the  walls,  and  down  the  walls  to  its  starting-point,  again 
to  repeat  the  round. 

Stoves  as  Ventilators.  —  If  there  is  an  opening  at  the 
top  of  the  room,  heated  air  will  escape  through  it.  Often 
the  heat  is  used  to  warm  upstairs  rooms  in  this  way.  If 
a  window  is  open  at  the  top,  some  heat  is  lost.  To  make 
up  for  the  losses  above  named,  and  also  for  the  air  that 
enters  the  stove  and  goes  up  the  chimney,  more  air  is 
drawn  in  usually  around  doors  and  windows.  It  is  espe- 
cially noticeable  where  there  are  openings  near  the  floor. 


Ventilation  and  Heating. 


109 


For  the  cold  air  is  heavier  than  the  warm  air  and  continu- 
ally pushes  the  warm  air  up  and  out  of  the  room  wherever 
it  can.  But  the  stove  does  not  send  as  much  air  up  the 
chimney  as  the  grate  does,  and  so  does  not  draw  in  as 
much  fresh  air.  It  is  therefore  not  a  good  ventilator. 
But  the  stove  gets  much  more  heat  from  a  given  amount 
of  fuel. 

A  Stove  and  Jacket.  —  In  some  cases  a  jacket  is  placed 
around  a  stove,  and  a  duct  from  the  outer  air  connects 


Fig-  62.    The  Unjacketed  Stove 


with  the  lower  part  of  the  space  inside  of  the  jacket  and 
outside  of  the  stove.  Then  as  the  air  heated  by  the  stove 
rises,  fresh  air  is  drawn  in  from  outside  to  be  warmed. 
In  this  case  the  direct  heat  from  the  stove  is  shut  off  from 
the  room.  Heat  radiates  in  straight  lines.  When  one 
holds  out  his  hands  beside  a  stove,  the  heat  he  receives 
is  radiant  heat.  Most  of  the  heat  from  a  grate  is  radiant 
heat.  But  in  a  jacketed  stove  the  heating  by  air  currents 
is  called  heating  by  convection. 


no  Physiology. 

The  Furnace.  —  A  furnace  is  practically  a  jacket  stove 
placed  in  a  basement.  Hot-air  furnaces  have  this  good 
feature,  that  they  are  all  the  time  sending  fresh  air 
into  a  room.  The  main  trouble  is,  the  air  is  usually  too 
dry.  There  should  be  in  the  furnace  a  pan  of  water  to 
furnish  moisture  to  the  air. 

Foul-air  Shafts  and  Fans.  —  Although  in  private  dwell- 
ings heated  by  furnaces  there  is  no  special  provision  for 
the  escape  of  foul  air,  there  is  ordinarily  sufficient  renewal 
of  the  air.  But  in  public  buildings  there  should  be  escape 
flues  for  foul  air.  Frequently  a  large  foul-air  shaft  is  built 
near  the  center  of  the  building,  and  a  small  stove  placed 
in  it  to  create  a  sufficient  up-current.  In  many  public 
buildings  the  currents  created  by  heat  are  not  strong 
enough  to  renew  the  air  properly.  Revolving  fans  are 
used,  which  force  the  air,  properly  heated,  into  the  room. 

Direct  Heating.  —  In  heating  by  steam  or  hot  water,  if 
the  radiators  are  placed  in  the  room  they  give  direct  or 
radiant  heat.  This  system  is  called  direct  heating.  It 
gives  direct  heat,  and  produces  air  currents  within  the 
room.  In  itself  it  has  no  provision  for  renewing  the  air. 

Indirect  Heating.  —  In  indirect  heating,  coils  of  steam 
or  hot-water  pipes  are  placed  in  air  shafts  which  lead  up 
to  the  rooms  above,  and  also  have  ducts  to  the  outside. 
As  the  air  is  heated  by  the  heat  of  the  pipes  it  rises  into 
the  rooms  above,  and  fresh,  cold  air  presses  in  through 
the  ducts,  to  be,  in  turn,  heated  and  sent  up.  If  there  is 
at  the  same  time  a  proper  escape  for  the  foul  air,  this 
makes  an  excellent  system. 

A  Combination  of  Direct  and  Indirect  Heating.  —  It  is  a 
good  plan  to  combine  direct  and  indirect  heating.  Where 


Ventilation  and  Heating.  1 1 1 

there  is  a  grate  in  a  room,  it  serves  very  well  as  a  foul-air 
shaft,  especially  when  there  is  a  fire  in  the  grate.  It  is 
well  to  have  the  flue  from  the  grate  in  the  same  chimney 
with  that  from  the  smoke-pipe  from  the  furnace,  as  then  the 
heat  from  the  smoke  will  cause  a  constant  up-draft  in  the 
grate  flue,  whether  there  is  a  fire  going  in  the  grate  or  not. 

With  a  grate,  in  private  houses,  there  is  ordinarily  no 
need  of  other  foul-air  shaft  for  any  room.  But  it  is  very 
desirable  to  have  at  least  some  "indirect"  heat,  so  that 
the  fresh  air  introduced  will  be  sufficiently  heated. 

If  the  introduction  of  air  is  thus  provided  for,  it  is  then 
safe  to  put  on  double  windows  and  make  the  cracks  around 
the  door  very  tight.  Without  any  special  provision  for  the 
renewal  of  the  air  these  cracks  are  the  means  of  safety.  In 
houses  heated  by  furnaces,  steam,  or  hot  water,  the  floor 
is  likely  to  be  warmer  from  the  escape  of  heat  from  the 
heater  itself,  and  from  pipes  or  air  ducts  under  the  floor. 

Double  Windows.  —  There  is  a  very  common  misunder- 
standing as  to  the  cold  felt  near  a  window  in  cold  weather. 
It  seems  that  air  is  entering;  but  a  little  reflection  will 
show  that  even  if  the  window  were  air-tight  this  effect 
would  be  produced,  for  the  air  near  the  window  is  cooled 
by  losing  heat  to  the  outer  air  through  the  glass.  The  air 
next  to  the  window,  thus  cooled,  is  heavier,  and  falls  to  the 
floor ;  and  if  there  is  any  source  of  heat  in  the  room,  this 
cold  air  will  pass  along  the  floor  to  that  source  of  heat,  up 
from  the  heating  body  to  the  ceiling,  and  across  the  ceil- 
ing, and  so  on  around  again.  There  may  thus  be  currents 
without  any  change  in  the  quality  of  the  air.  It  is 
economy  to  use  double  windows  and  prevent  the  loss  of 
heat  through  the  glass.  So  both  economy  and  comfort 
suggest  to  us  that  we  reduce  as  much  as  possible  cracks 
around  doors  and  windows, 'use  double  windows,  make 


H2  Physiology. 

vestibules  at  entrances,  and  build  special  ducts  by  which 
fresh  air  may  enter,  and  heat  it  properly  on  its  way  in. 

To  Air  a  Room  without  Draft  — To  introduce  fresh  air 
into  a  room  without  having  a  draft,  a  good  plan  is  to  get  a 
board  four  inches  wide  and  as  long  as  the  width  of  the 
window  sash.  Raise  the  window,  place  the  board  under 
it  and  shut  the  window  down  upon  the  board.  This  will 
allow  air  to  enter  between  the  upper  and  lower  sash,  and 
it  will  be  directed  toward  the  ceiling.  This  is  of  double 
advantage;  in  the  first  place,  it  does  not  strike  any  one 
directly ;  in  the  second  place,  it  mingles  with  the  warm  air 
of  the  upper  part  of  the  room  before  it  reaches  us. 

Wearing  Slippers.  —  In  rooms  heated  by  stoves  or  grates 
there  is  always  more  or  less  cold  air  moving  along  the 
floor.  Wearing  slippers  in  such  a  room  causes  many  per- 
sons to  take  cold.  The  ankles  have  been  warmly  dressed 
through  the  day  and  while  the  person  was  more  active. 
Especially  if  one  is  studying  there  is  a  tendency  to  draw 
the  blood  away  from  the  feet  and  make  them  cold.  It  is 
restful,  in  the  evening,  to  take  off  the  shoes  that  have  been 
worn  during  the  day;  but,  for  most  persons,  it  would  be 
better  to  put  on  a  pair  of  loose  shoes  so  the  ankles  will  be 
protected.  The  floor  is  usually  the  coolest  place  in  a  room. 
In  sitting  in  a  room  heated  by  a  grate,  or  stove,  the  head 
usually  gets  the  most  heat,  and  the  feet  the  most  cold,  just 
the  reverse  of  what  it  should  be.  If  much  heat  escapes 
from  a  furnace,  the  floor  may  be  warm.  Those  who  use 
stove  heat  in  loosely  built  houses,  learn  to  keep  the  feet  up 
on  a  stool  when  sitting  in  a  room  in  cold  weather. 

Ventilation  of  Cellars.  —  The  cellar  is  the  source  of  con- 
tamination of  the  air  of  many  houses.  Of  course  a  cellar 


Ventilation  and  Heating.  I  T  3 

ought  to  be  dry,  well  lighted,  and  well  ventilated.  But 
since  many  of  them  are  dark  and  ill  ventilated,  especial 
care  should  be  taken  to  keep  them  dry.  Fruit  and  vege- 
tables should  not -be  allowed  to  decay  in  the  cellar.  On 
entering  many  houses  one  can  at  once  detect  the  smell 
of  decaying  potatoes  and  other  vegetables.  Such  material 
should  be  promptly  removed.  The  best  time  to  ventilate 
a  cellar  is  at  night,  for  if  the  cellar  windows  are  opened 
in  the  day  time,  the  entering  air  will  deposit  moisture, 
making  the  cellar  more  damp  instead  of  dryer. 

Summary.  —  i.    Lung  diseases  usually  accompany  close  confinement, 
but  are  rare  with  those  living  in  the  open  air. 

2.  Air  in  rooms  needs  constant  renewal. 

3.  Grates  are  good  ventilators,  but  not  economical  heaters. 

4.  Stoves  are  economical  heaters,  but  poor  ventilators.     Both  grates 
and  stoves  heat  very  unevenly. 

5.  All  crowded  rooms,  as  schoolrooms  and  churches,  need  special 
inlets  for  fresh  air  and  outlets  for  foul  air. 

6.  The  most  common  means  of  withdrawing  the  air  is  by  foul-air 
shafts.     Heat  is  the  force  relied  on,  but  the  removal  of  foul  air  is  usually 
inadequate,  on  account  of  the  slowness  of  the  current  or  the  narrowness 
of  the  outlet,  or  both  combined. 

7.  Fans  are  much  more  certain  to  be  effectual. 

8.  Steam  and  hot  watsr  may  heat  directly  (by  radiation)  or  indirectly 
(placed  in  flues).     It  is  best  to  combine  direct  and  indirect  heating. 

Questions.  —  i .    How  can  we  renew  the  air  of  a  room  without  having 
unpleasant  drafts? 

2.  Should  bedroom  windows  be  open  at  night?     Is  night  air  bad? 

3.  What  dangers  in  the  use  of  hard  coal  ? 

4.  Should  there  be  a  damper  in  the  smoke-pipe  of  a  hard  coal  stove? 

5.  What  do  miners  mean  by  "  choke  damp  "  ? 

6.  Compare  stove  and  furnace  heating. 

7.  Compare  heating  by  steam  and  by  hot  water. 

8.  Read  about  the  "  Black  Hole  of  Calcutta." 


CHAPTER   XII. 
DUST  AND  BACTERIA. 

The  Air  is  washed  by  Rain  or  Snow.  —  Every  one  will 
recall  how  delightfully  refreshing  the  air  is  after  a  rain  or 
a  snowstorm.  This  is  not  due  merely  to  the  fact  that  the 
air  is  cool.  It  is  clean  because  it  has  been  washed.  The 
rain  and  snow  absorb  most  of  the  various  impure  gases 
that  are  in  the  air.  The  raindrops  and  snowflakes  also 
bring  down  with  them  many  particles  of  dust  that  were 
floating  in  the  air.  Take  some  of  the  snow  that  has  fallen 
in  a  town.  It  looks  pure  in  its  almost  dazzling  whiteness. 
But  melt  some  of  it,  and  you  will  usually  find  that  the 
water  has  an  inky  tinge,  showing  that  as  the  flakes  sifted 
down  through  the  air  they  caught  myriads  of  particles  of 
dust. 

The  Sources  of  Dust.  —  Where  soft  coal  is  used  to  any 
large  extent  it  is  one  abundant  source  of  this  dust.  In 
summer  dust  has  many  sources.  The  dust  that  blows  into 
your  face,  and  perhaps  into  your  mouth,  may  be  made  of 
dry  soil.  Take  a  dry  clod  and  drop  it ;  it  falls  quickly  to 
the  ground.  Crush  it  in  your  hand  before  dropping  it,  and 
much  of  it  floats  in  the  air  for  some  time.  Any  substance 
that  is  easily  dried  and  reduced  to  powder  may  form  part 
of  the  common  dust.  The  dust  that  you  wipe  from  your 
eye,  or  is  caught  by  the  mucus  of  the  nasal  passages,  may, 
instead  of  being  made  of  clean  soil,  be  from  the  excreta  of 
horses,  decayed  leaves,  wood,  grass,  etc.  Indoors  we  are 

114 


Dust  and  Bacteria.  1 1 5 

constantly  making  dust  by  wearing  out  our  clothes.  Many 
of  the  tiny  particles  that  we.  see  floating  in  the  sunbeams 
are  bits  of  cotton  or  woolen  fibers.  Shake  any  garment  in 
a  beam  of  light  to  see  how  much  dust  is  given  off.  The 
worn-off  particles  of  our  shoes,  books,  floors,  all  contribute 
to  the  ever-present  dust. 

The  Effect  of  Dust  on  the  Lungs.  —  This  dust  is  irritating 
to  the  lungs  and  respiratory  passages.  There  is  provision, 
as  we  have  seen,  for  catching  and  getting  rid  of  a  good 
deal  of  it.  But  still  much  is  taken  into  the  lungs.  Exam- 
ination shows  that  the  lungs  have  many  black  specks  from 
particles  of  carbon,  etc.,  that  have  become  lodged,  and  are 
of  no  benefit,  to  say  the  least. 

Composition  of  Live  Dust.  —  Bad  as  this  dead  dust  is,  the 
injury  from  it  is  slight  compared  to  that  from  live  dust. 
We  know  that  certain  seeds  float  in  the  air,  carried  along 
by  the  wind.  But  these  are  comparatively  heavy,  and  soon 
sink  to  the  ground. 

We  all  know  pollen.  At  certain  seasons  it  forms,  in  the 
vicinity  of  cornfields,  for  instance,  a  considerable  part  of 
the  dust.  This  is  alive.  It  will  grow  if  it  falls  on  the 
stigma  of  the  right  plant  at  the  right  time.  Such  dust  will 
not  grow  in  our  bodies.  We  do  not  furnish  a  soil  in  which 
it  can  grow.  It  merely  adds  to  the  amount  of  irritating 
dust. 

Puffballs  and  Molds. — We  have  seen  puffballs  give  off 
a  cloud  of  dust  when  they  are  crushed.  So,  too,  from  a 
patch  of  mold,  when  brushed,  we  often  see  a  little  cloud  of 
dust.  This  dust  is  composed  of  live  spores  that  will  grow 
in  suitable  places  and  conditions. 

Yeast.  —  If  we  set  a  tumbler  of  cider  on  a  table  in  a 
warm  room,  in  a  few  days  it  ferments.  This  is  due  to 


1 1 6  Physiology, 

a  kind  of  living  germ  or  spore  that  has  gotten  into  it  from 
the  dust  on  the  fruit  before  it  was  crushed,  or  from  dust 
in  the  room.  Boil  the  cider  to  kill  the  spores  already  in 
it,  and  cork  it  securely  so  that  air  cannot  get  at  it,  and  it 
will  not  ferment.  These  are  a  few  instances  of  kinds  of 
living  dust  that  do  not  affect  human  beings  any  more 
than  so  much  dead  matter. 

Disease  Germs.  —  But  there  are  floating  in  the  air  many 
kinds  of  spores  that  may  grow  in  our  bodies.  We  know 
that  many  of  our  contagious  diseases  are  due  to  the  growth 
of  some  of  these  spores  in  our  bodies.  Our  bodies  are  a 
good  soil  for  certain  germs.  The  germs  that  cause  con- 
sumption, typhoid  fever,  Asiatic  cholera,  erysipelas,  diph- 
theria, lockjaw,  the  grippe,  malaria,  yellow  fever,  and  blood 
poisoning  are  well  known.  Microscopists  know  them  when 
they  see  them  as  readily  as  we  know  peas  from  beans. 
And  it  is  proved  beyond  all  doubt  that  these  germs  get 
into  our  bodies  by  being  breathed  in,  or  by  being  eaten  in 
food,  or  in  drinking  water,  or  by  introduction  into  the 
blood  in  wounds.  We  have  reason  to  believe  that  small- 
pox, measles,  mumps,  whooping-cough,  and  scarlatina  are 
caused  by  germs,  but  these  diseases  have  not  been  studied 
so  successfully. 

How  to  avoid  Germs.  —  How  can  we  avoid  or  get  rid 
of  dusts  of  these  kinds  ?  To  exterminate  any  plant,  we 
try  to  keep  the  seeds  from  ripening,  and  to  kill  all  that  do 
ripen.  Let  us  take  a  case  that,  while  not  pleasant  to  think 
about,  is  too  terribly  true  to  allow  of  being  called  an  imag- 
ined case. 

The  Danger  from  Consumption. — A  consumptive  spits 
on  the  pavement.  In  this  sputum  are  probably  hundreds, 
if  not  thousands,  of  germs  known  as  bacilli  (Bacillus  tuber- 


Dust  and  Bacteria. 


117 


culosis).  They  are  alive.  Now,  so  long  as  they  remain 
on  the  pavement  they  do  no  harm.  The  sputum  dries. 
But  the  bacilli  are  not  killed  by  drying.  With  other  dry 
material  from  the  pavement  they  form  part  of  the  common 
dust.  Any  one  of  us  may  breathe  some  of  this  kind  of  mat- 
ter any  day,  for  there  are  persons  afflicted  with  this  dreaded 


Bacillus  of  Diphtheria  (x  1000) 


Bacillus  of  Tuberculosis  (x  1000) 


Bacillus  of  Typhoid   Fever  (x  1200) 
showing  flagellums 


Bacillus  (Spirillum)  of  Asiatic  Cholera  Bacillus  of  Hog  Cholera  (x  1000) 

Fig.  63.     Different  Kinds  of  Bacilli. 

disease  in  every  community.  Our  bodies  furnish  the  very 
best  soil  for  the  germs.  We  do  not  need  to  go  into  the 
street  to  be  exposed.  These  germs  may  be  brought  into 
the  most  cleanly  houses  upon  one's  clothing,  or  by  the  wind. 

How  to  avoid  the  Danger.  —  Of  course,  all  such  material 
known  to  be  dangerous  should  be  destroyed.  If  those 
suffering  from  such  diseases  were  careful  to  burn  all  such 
matter,  in  time  we  might  stamp  out  the  diseases.  But  so 


1 1 8  Physiology. 

long  as  people  spit  upon  the  floors  and  pavements  it  will 
be  difficult  to  prevent  the  spread  of  such  germ  diseases. 

In  hospitals  such  matters  are  now  looked  after  with  the 
greatest  care,  and  in  private  houses  where  there  is  intelli- 
gence on  these  subjects.  Many  of  the  railroad  and  street 
car  companies  now  forbid  spitting  on  the  floors  of  cars 
and  stations,  not  merely  because  it  is  uncleanly,  but  be- 
cause it  is  a  means  of  spreading  infectious  diseases. 

Bacteria.  —  These  disease  germs  are  the  smallest  and 
simplest  of  living  things.  They  are  plants ;  and  while  all 
of  them  that  are  well  known  have  their  scientific  names, 
just  as  the  larger  plants  have,  they  are  all  included  in  one 
general  group  called  Bacteria. 

How  to  avoid  Dust.  —  We  need  to  learn  a  good  deal 
more  about  avoiding  and  destroying  dust,  and  the  things 
that  make  it.  Towns  and  cities  need  more  sprinkling  to 
keep  the  dust  down.  Much  more  of  the  refuse  and  street 
sweepings  and  cleanings  ought  to  be  burned.  The  dust  of 
a  house  should  always  be  burned,  as  we  know  not  what 
germs  of  disease  may  be  in  it.  If  we  burn  it,  we  shall 
surely  not  have  to  sweep  up  that  dust  again.  If  we  send 
it  out  of  doors  it  may  come  back,  and  we  may  have  to 
handle  it  again  and  again. 

Sweeping  and  Dusting.  —  So  far  as  possible  let  us  avoid 
things  that  make  dust.  When  we  sweep  a  carpet,  a  con- 
siderable share  of  the  dust  comes  from  the  carpet  itself, 
especially  if  the  carpet  is  old.  Curtains  and  tapestries  of 
nearly  all  sorts  not  only  hold  dust,  but  contribute  a  good 
deal  to  it.  Those  who  write  on  such  subjects  recommend 
hard  wood  floors  with  rugs  instead  of  carpets.  The  rugs 
can  be  taken  out  of  doors  and  shaken,  and  the  floors  wiped 
with  a  moist  cloth,  so  that  little  dust  is  left  floating  in  the 


Dust  and  Bacteria.  119 

air  of  the  room.  Compare  this  with  the  condition  after  the 
ordinary  sweeping  of  a  carpeted  room  with  the  common 
broom.  The  dust  fills  the  air,  only  to  settle  back  on  the 
floor  and  furniture.  Then  comes  the  so-called  dusting. 
But  do  we  get  rid  of  the  dust  ?  For  those  who  cannot  have 
hard  wood  floors  a  most  excellent  substitute  is  oilcloth  or 
linoleum. 

Sweeping  the  Sick  Room.  —  The  improved  carpet 
sweepers  are  not  only  convenient,  but  sanitary.  Many  a 
well-meaning  person  will  sweep  a  carpet  in  a  sick  room 
with  an  ordinary  broom  when  the  patient  is  suffering  from 
lung  disease,  thoughtless  of  the  fact  that  a  little  dust  on 
the  floor  is  of  much  less  significance  than  dust  in  the  air 
we  breathe.  No  one  likes  dust  on  the  floor,  but  better  a 
thousand  times  there  than  in  our  lungs. 

Lung  Diseases.  —  Statistics  seem  to  show  that .  one 
seventh  of  the  deaths  among  the  civilized  races  is  due  to 
lung  diseases.  The  best  authorities  are  now  agreed  that 
consumption  is  not  hereditary.  But  it  appears  that  there 
may  be  inherited  a  tendency  to  this  disease,  so  that,  if  ex- 
posed, such  persons  are  more  likely  to  contract  the  disease 
than  others.  Probably  anything  that  lowers  the  general 
vitality  makes  the  system  more  ready  to  yield  to  any  of 
these  contagious  diseases.  We  have  all  noticed  what  a 
difference  there  is  among  individuals  in  the  readiness  with 
which  they  "catch"  contagious  diseases. 

How  to  ward  off  Contagious  Diseases.  —  A  good  general 
condition  of  the  body  helps  greatly  to  ward  off  diseases  of 
this  nature.  A  cheerful  condition  of  mind  and  body  should 
be  cultivated.  In  times  of  widespread  contagious  disease, 
if  one  is  terrified  into  the  belief  that  he  is  going  to  have 
the  disease,  he  is  more  likely  to  take  it.  Thorough  clean- 


I2O  Physiology. 

liness,  plenty  of  direct  sunshine,  care  in  diet,  and  the 
keeping  of  the  body  in  good  tone,  reduce  the  chances  of 
"taking"  contagious  diseases.  An  open-air  life,  abundant 
nutritious  food,  and  freedom  from  anxiety  are  probably  the 
best  cures  for  the  first  stages  of  consumption. 

Destruction    of    Germs   by   Colorless    Corpuscles.  —  The 

colorless  blood  corpuscles  may  take  these  germs  of  disease 
into  their  substance,  and  destroy  or  change  them  so  that 
the  disease  is  warded  off.  In  other  words,  they  may  be 
compared  to  a  cat  that  catches  and  eats  the  mice  which 
invade  a  house. 

Germs  killed  by  Plasma.  —  Sometimes  the  blood  con- 
tains a  substance  that  kills  or  prevents  the  action  of  dis- 
ease germs.  Such  a  substance  is  called  anti-toxin,  which 
means  a  counteracting  poison.  But  the  blood  of  most 
persons  does  not  naturally  contain  anti-toxin,  and  so,  if  the 
disease  germs  gain  entrance,  the  disease  follows. 

Danger  of  getting  Germs  into  Wounds.  —  There  is  danger 
of  introducing  germs  of  disease  in  so  simple  an  act  as  pick- 
ing out  a  sliver  with  a  pin.  If  such  germs  happen  to  be 
on  the  point  of  the  pin,  the  mischief  is  easily  done.  Great 
care  should  be  taken  in  any  such  operation  to  use  a 
thoroughly  clean  needle  or  lancet  Formerly  any  surgical 
operation  that  required  opening  the  body  cavity,  either  the 
chest  or  the  abdomen,  usually  resulted  in  death.  Now- 
adays such  operations  are  commonly  successful,  because 
surgeons  sterilize  their  instruments,  hands,  and  everything 
used  about  the  work.  They  kill  any  germs  that  might 
be '  introduced.  In  "a  word,  they  have  learned  to  be 
clean. 

In  caring  for  a  patient  ill  of  any  germ  disease,  one  should 
wash  the  hands  in  some  disinfectant,  such  as  chlorid  of 


Dust  and  Bacteria.  121 

lime,  and  should  not  touch  the  fingers  to  the  lips;  igno- 
rance of  these  simple  rules  has  caused  many  deaths. 

Malaria  and  Yellow  Fever.  —  Malaria  is  due  to  an  animal 
germ  (not  a  bacterium)  that  gets  into  the  blood.  It  is 
introduced  by  mosquitoes  that  have  bitten  persons  whose 
blood  contains  these  germs.  The  same  is  true  of  yellow 
fever. 

The  Bacteria  of  Putrefaction.  —  Besides  the  disease- 
producing  bacteria,  there  are  others  that  cause  decay  and 
putrefaction  of  various  kinds.  They  cause  foods  to  "  spoil," 
milk  to  turn  sour,  butter  to  become  rancid,  etc. 

While  these,  bacteria  do  not  cause  disease  in  the  human 
body,  they  often  make  food  poisonous.  The  cases  fre- 
quently reported  of  poisoning  from  eating  ice  cream, 
cheese,  sausage,  etc.,  are  in  many  cases  due  to  bacteria 
in  them.  We  should,  in  the  first  place,  be  careful  to  get 
good,  fresh  material.  In  the  second  place,  it  should  be  so 
kept  as  to  prevent  the  introduction  and  development  of 
bacteria  in  it.  Bacteria  need  heat  and  moisture  for  their 
growth  just  as  higher  plants  do. 

The  Preservation  of  Foods.  —  So  our  principal  modes  of 
keeping  foods  from  spoiling  are  to  keep  them  in  a  cold 
place,  or  to  dry  them.  Or  we  heat  them,  and  shut  them 
away  from  the  air,  as  in  our  various  modes  of  canning  and 
preserving  foods.  Salting  and  smoking  meats,  etc.,  pre- 
serve them  by  preventing  the  growth  of  bacteria.  Cold 
does  not  usually  kill  bacteria.  So  milk  that  has  been  kept 
in  a  refrigerator,  and  that  seems  sweet,  may  have  in  it  a 
stock  of  bacteria,  and  after  we  drink  the  milk  the  heat  of 
our  bodies  favors  their  development.  If  milk  is  heated  to 
160°  or  170°  F.,  any  germs  of  tuberculosis  present  will  be 
9 — PHY 


122  Physiology. 

killed.  Boiled  milk  is  less  readily  digested,  and  it  is  not 
necessary  to  boil  it  to  kill  most  kinds  of  germs  that  it  may 
contain. 

Summary.  —  I .  Dust  as  mere  dry,  dead  matter  is  irritating. 

2.  Disease  germs  may  form  part  of  the  dust  of  the  air. 

3.  Most  of  our  contagious  diseases  are  known  to  be  due  to  bacteria. 

4.  Burning  is  the  surest  method  of  destroying  germs. 

5.  Carpets,  tapestries,  and  cloth-upholstered  furniture  add  largely 
to  the  dust  in  houses. 

6.  Putrefaction  is  caused  by  bacteria. 

7.  Preservation  of  food  depends  on  destroying,  excluding,  or  retard- 
ing the  growth  of  the  bacteria  of  putrefaction. 

Questions.  —  I.  Is  the  air  in  the  mountains  or  on  the  seashore  better 
than  elsewhere? 

2.  What  regions  are  recommended  for  consumptives ?     Why? 

3.  How  is  milk  sterilized? 

4.  Why  do  people  seldom  take  cold  while  "  camping  out  "? 

5.  Why  are  the  "steel  grinders,"  in  factories,  short-lived? 

6.  What  occupations  should  be  avoided  by  one  who  is  predisposed 
to  consumption  ? 

7.  What  are  some  of  the  occupations  suitable  to  those  predisposed 
to  consumption? 


CHAPTER  XIII. 
EXCRETION. 

The  Formation  of  Waste  Matter  in  the  Body.  —  All  the 

force,  or  energy,  of  the  body  is  produced  by  oxidation  in 
the  tissues;  thought  by  oxidation  in  the  brain;  motion  by 
oxidation  in  the  muscles;  and  heat,  wherever  oxidation 
goes  on.  This  oxidation  produces  waste  matter  in  our 
bodies  just  as  we  have  seen  that  oxidation  in  a  stove 
produces  waste  matter. 

The  Need  of  Removal  of  Waste.  —  When  we  waken  on  a 
cold  winter  morning  we  are  likely  to  find  that  the  fire  in 
our  hard  coal  stove  has  burned  low.  Not  enough  heat  is 
given  out.  What  is  the  trouble?  Is  it  merely  that  more 
coal  is  needed  ?  We  put  another  hod  of  coal  in  the  maga- 
zine (though  usually  some  remains).  Does  this  bring  the 
desired  result?  No.  We  open  the  draft.  Is  this  suffi- 
cient? It  is  not.  We  must  shake  down  the  grate  and 
clean  out  the  clinkers.  The  removal  of  waste  is  as  neces- 
sary as  the  addition  of  a  fresh  supply  of  fuel.  In  this  case 
more  necessary,  for  no  amount  of  fuel  will  do  any  good  so 
long  as  the  ashes  shut  off  the  draft.  In  our  bodies  the 
removal  of  waste  is  still  more  important,  because  waste 
matter  not  only  clogs  the  system,  but,  if  present  in  any 
great  amount,  acts  as  a  poison  to  the  tissues. 

The  Skin  throws  off  Waste  Matter.  —  The  skin  is 
constantly  throwing  off  waste  matter  called  sweat,  or 
perspiration. 

123 


124 


Physiology. 


Experiment  to  show  Insensible  Perspiration.  —  Thrust  the  hand  into 
a  cold  glass  jar.  Note  the  moisture  that  soon  gathers  on  the  inside  of 
the  jar  from  the  insensible  sweat  of  the  hand.  A  common  fruit  jar  will 
do  for  a  small  hand,  but  a  candy  jar  is  better,  having  a  larger  mouth  and 
clear  glass. 

The  Structure  of  the  Skin.  —  The  skin  has  two  layers, 
the  inner,  or  dermis,  and  the  outer,  or  epidermis.  The 

epidermis  is  thick 
over  the  palms  and 
soles;  elsewhere  it 
is  thin.  The  skin  is 
much  thicker  than 
we  would  naturally 
suppose,  and  makes 
one  fifteenth  of  the 
weight  of  the  body. 

The  Epidermis.  — 

The  epidermis  con- 
Cells  sists  of  many  layers 
of  cells  packed 
*Buib  closely  together. 
The  deepest  cells 
may  be  compared  to 
grapes  with  their  cell 
walls  'plumply  filled  out  with  the  liquids  of  the  cell.  Sup- 
pose for  the  inner  layer,  grapes  set  on  end,  and  so  closely 
packed  together  as  to  press  each  other  more  or  less  flat  on 
the  sides.  Above  these  are  cells  less  closely  pressed,  more 
nearly  spherical ;  then  cells  with  less  liquid  in  them,  and 
somewhat  shrunken,  like  raisins.  Then  still  dryer  cells 
flattened  parallel  with  the  surface  of  the  skin.  And,  last, 
in  the  outer  part,  layers  of  cell  walls,  dry  and  empty,  pressed 
flat  like  empty  grape  skins.  These  flat  cell  walls  come  off 


Fat 


Fig.  64.    Vertical  Section  of  the  Skin. 


Excretiorio 


125 


in  flakes  (those  from  the  scalp  are  called  dandruff)  from 
all  the  surface  of  the  skin,  and  new  cells  are  continually 
formed  in  the  deeper  layers. 


Mouth  of  Sweat  Duct 


Horny  Epider- 
mis 


Soft  Laye. 


Papilte 


Dermis 


rtery 


Fig.  65.    Section  of  Epidermis,  showing  Papilla.     (Highly  magnified.) 

The  Color  of  the  Skin.  —  The  coloring  matter,  or  pig- 
ment, of  the  skin  lies  in  the  deeper  layer  of  the  epidermis. 
In  albinos  the  pigment  is  wanting.  In  persons  with  fair 
skin  it  is  small  in  amount,  in  dark  skins  more  abundant. 
Where  the  pigment  is  scattered  irregularly  it  causes 
freckles,  etc. 

A  Blister.  —  A  blister  is  caused  by  separating  the  outer, 
harder  layer  of  the  epidermis  from  the  inner,  softer,  darker 
layer  of  the  epidermis,  as  at  B,  in  Fig.  64.  Serum,  or 
blood,  fills  the  space  between  the  separated  layers. 


126  Physiology. 

The  Dermis. — The  dermis  consists  chiefly  of  tough, 
interlacing  fibers.  Hence  the  strength  and  durability  of 
leather,  which  is  the  dermis  preserved  and  prepared.  The 
epidermis  is  usually  removed  in  tanning.  The  dermis  is 
richly  supplied  with  blood  capillaries  and  lymph  capillaries, 
but  the  epidermis  has  neither. 

Papillas.  —  The  outer  surface  of  the  dermis  has  many 
conical  elevations,  each  of  which  is  called  a  papilla.  Over 
most  of  the  skin  they  do  not  show  on  the  outer  surface,  as 
the  epidermis  fills  in  the  spaces  between  them,  but  is,  itself, 
smooth  on  the  outside.  On  the  palms  and  soles  the  papillas 
are  in  rows,  and  these  rows  are  indicated  by  the  ridges. 

Hairs.  —  Hairs  are  outgrowths  of  the  epidermis,  but  are 
deeply  embedded  in  the  dermis.  They  are  supplied  with 
blood  at  the  tip  of  the  root,  where  the  growth  takes  place. 
The  exposed  part  of  the  hair  does  not  contain  blood  and  is 
not  sensitive.  (See  Fig.  64.) 

Hair-muscles.  —  There  are  small  muscles  connected  with 
the  roots  of  the  hairs,  by  which  the  hair  may  be  slightly 
moved.  In  the  lower  animals  this  power  is  much  more 
used,  as  when  the  hair  is  made  to  stand  erect  on  the  back 
or  tail  of  an  angry  cat  or  dog.  The  action  of  these  muscles 
when  frightened  is  what  gives  a  peculiar  feeling  in  the 
scalp,  and  to  express  strong  fright  we  say,  "  It  made  his 
hair  stand  on  end." 

Oil  Glands.  —  The  oil  glands  of  the  skin  are  distributed 
over  all  the  surface  except  the  palms  and  soles.  The  oily 
matter  is  usually  poured  out  around  the  hairs  as  they 
emerge  from  the  skin ;  but  some  of  the  ducts  open  on  the 
skin  away  from  a  hair.  The  oil  serves  to  soften  the  skin 
and  hair  and  keep  them  from  becoming  too  dry.  (See 
Fig.  64.) 


Excretion.  1 27 

Nails.  —  The  nails,  like  the  hair,  are  outgrowths  of  the 
epidermis.  At  the  base  the  nail  is  supplied  with  blood,  and 
here  it  grows.  It  is  alive,  hence  this  part  is  called  the 
quick  ;  but  at  the  outer  surface  and  the  tip  it  is  dead. 

Examination  of  the  Skin  with  a  Lens.  —  Place  a  linen  tester,  or  other 
hand  magnifier,  over  the  palm,  and  note  the  sweat  pores  or  openings  of 
the  ducts  of  the  sweat  glands.  Count  the  pores  within  the  square  shown. 
Measure  this  square,  and  then  estimate  the  number  of  sweat  glands  to  a 
square  inch  of  the  palm. 

The  Sweat  Glands.  —  The  sweat  glands  are  minute  tubes 
whose  inner  ends  are  closed,  and  whose  outer  ends  open 
upon  the  surface  of  the  skin.  The  tube  going  inward  pur- 
sues a  corkscrew-like  course  through  the  epidermis,  then 
becomes  straighter,  and  is  coiled  up  in  a  ball  in  the  deeper 
layer  of  the  dermis,  or,  more  often,  in  the  connective  tissue 
just  beneath  the  skin.  (See  Fig.  64.)  The  cells  forming 
the  walls  of  the  coiled  part  are  different  from  those  of  the 
duct,  or  straighter  part  of  the  tube.  As  the  blood  flows 
through  the  capillaries  of  the  skin  it  gives  off  lymph.  In 
this  lymph  are  waste  matters  brought  from  the  muscles 
and  other  tissues  that  have  been  at  work.  The  sweat 
glands  absorb  this  waste  matter,  with  considerable  water, 
and  pass  it  out  to  the  surface. 

Composition  of  Sweat.  —  Sweat  is  mostly  water.  About 
one  per  cent  is  solid  matter,  including  salt  and  certain 
matter  which  like  the  organic  waste  matter  from  the  lungs, 
easily  putrefies.  Sweat  varies  greatly  in  its  wateriness  and 
hence  in  the  relative  amount  of  solid  matter  contained. 
Ordinarily  the  sweat  is  evaporated  as  fast  as  it  is  poured 
out.  In  distinction  from  this  insensible  perspiration,  there 
is  the  sensible  perspiration  —  when  it  accumulates  enough 
to  be  seen.  These  are  not  two  kinds  of  sweat,  but  it  is  con- 
venient to  distinguish  between  the  visible  and  the  invisible. 


128  Physiology. 

The  Amount  of  Perspiration.  —  There  is  about  one  quart 
in  twenty-four  hours.  It  varies  with  ( i )  The  temperature 
and  dryness  of  the  air.  (2)  The  condition  of  the  blood, 
e.g.  if  watery  from  drinking  much  water.  (3)  Muscular 
exercise. 

Gland  Action  and  Blood  Supply. — The  sweat  glands,  like 
all  glands,  are  largely  dependent  on  the  amount  of  blood 
supply.  In  exercising,  the  skin  is  usually  redder  from  the 
greater  supply  of  blood,  and  at  the  same  time  the  glands 
are  more  active,  for  during  exercise  and  for  some  time 
afterward  there  is  more  waste  matter  to  be  thrown  out. 

Control  of  the  Sweat  Glands.  —  But  the  activity  of  the 
gland  is  not  a  mere  filtering  process ;  it  is  not  always  in 
proportion  to  the  amount  of  liquid  present.  There  may 
be  a  cold  sweat,  i.e.  when  the  skin  is  pale.  This  usually 
is  due  to  excitement  or  emotion,  which  shows  that  the 
action  of  glands  is  under  the  control  of  the  nervous  system. 

Sweat  Glands  are  Excretory.  —  The  sweat  glands  rid  the 
body  of  certain  waste  matters,  and  are  therefore  called 
excretory  glands.  A  sweat  gland  is  a  simple  gland. 

Distribution  of  Sweat  Glands.  —  The  sweat  glands  are 
thickly  distributed  over  the  whole  surface  of  the  body,  but 
are  especially  numerous  and  large  on  the  palms  and  soles. 
In  the  armpits  the  glands  are  also  large. 

Regulation  of  the  Temperature  of  the  Body.  —  It  is  a  very 
striking  fact  that,  except  in  disease,  the  temperature  of  the 
body  varies  only  a  little  from  98.5°  F.  in  winter  and 
summer,  during  exercise  and  rest.  The  rate  of  producing 
heat  varies  greatly.  The  rate  of  giving  off  heat  must 
therefore  vary  accordingly. 


Excretion.  1 29 

The  Body  gives  off  Heat.  —  In  considering  the  regulation 
of  the  temperature  of  the  body,  we  must  bear  in  mind  that 
the  body  is  surrounded  by  air  that  is  almost  always  con- 
siderably cooler  than  itself.  The  body  is  therefore  almost 
always  giving  off  heat.  Our  clothes  do  not  warm  us ;  we 
warm  them,  and  they  keep  us  from  warming  the  air  too 
fast,  i.e.  they  keep  us  from  losing  too  much  heat.  Indoor 
air  in  winter  should  be  kept  at  about  68°  F.  by  artificial 
heat.  This  air  does  not  warm  us ;  we,  being  about  30°  F. 
warmer,  are  warming  it. 

Ways  of  giving  off  Heat. — The  skin  gives  off  heat  by — 

1 .  Radiation :  heat  is  given  off  in  every  direction. 

2.  Conduction:   whatever  we  touch  that  is  cooler  than 
our  bodies  is  warmed.     We  warm  chairs,  clothing,  etc. 

3.  Convection:    the   air    in    contact   with    the   skin    is 
warmed  and  rises.     Our  bodily  heat  is  thus  carried  off  by 
convection. 

4.  Evaporation:  the  evaporation  of  sweat  is  the  most 
important  factor  in  regulating  the  heat  of  the  body.     Any 
liquid  in  evaporating  absorbs  heat.     The  cooling  effect  of 
alcohol,  ether,  or  cologne  on  the  skin  is  due  to  the  fact 
that  heat  is  taken  from  the  skin  in  converting  the  liquid 
into  a  gas. 

Experiment  in  Evaporation.  —  With  a  medicine  dropper  put  a  drop 
of  cologne  on  the  back  of  the  hand.  Note  two  facts  :  (i)  it  produces  a 
cooling  effect ;  (2)  the  liquid  quickly  disappears. 

Practical  Applications  of  this  Principle.  —  We  sponge  a 
feverish  patient  to  reduce  his  temperature.  The  cooling 
effect  is  due  not  so  much  to  the  coolness  of  the  water  itself 
as  to  the  absorption  of  heat  from  the  skin  in  evaporating 
the  water.  We  sprinkle  the  floor  in  hot  weather  and  thus 
cool  the  air  of  the  room. 


130  Physiology. 

Heat  and  Exercise. — When  we  exercise  we  produce  more 
heat ;  we  sweat  more ;  more  heat  is  taken  from  the  body 
to  evaporate  this  sweat.  If  we  are  not  exercising  and  are 
in  cooler  air,  we  sweat  less,  and  less  heat  is  given  off. 
When  we  exercise  there  is  more  blood  in  the  skin,  and 
more  heat  is  given  off  by  radiation,  convection,  and  con- 
duction. When  we  exercise  less,  the  skin,  especially  in 
cool  air,  is  paler,  i.e.  has  less  blood  in  it,  and  heat  is  econo- 
mized. Thus  the  temperature  of  the  body  is  kept  uniform. 

Distribution  of  Heat  in  the  Body.  —  If  more  heat  is  pro- 
duced in  one  part  of  the  body  than  in  others,  the  circula- 
tion of  the  blood  tends  to  equalize  the  temperatures  of  the 
different  parts.  So,  too,  if  one  part  is  cooled,  i.e.  is  losing 
heat  faster  than  others,  the  blood  brings  heat  from  other 
organs  to  that  part.  If  the  hands  and  feet  are  exposed  to 
cold,  it  may  do  little  good  to  have  the  rest  of  the  body  well 
covered.  A  pair  of  wristers  and  a  pair  of  leggings  may 
often  add  more  to  one's  comfort  than  a  heavy  overcoat. 

Regulation  of  Temperature  by  Clothing.  —  In  cold  weather 
we  put  on  more  clothing  and  select  non-conductors  of 
heat,  as  woolen,  leather,  and  fur.  Many  authorities  recom- 
mend light  woolen  for  summer  wear,  since  with  it  we  do 
not  cool  off  so  rapidly. 

Regulation  of  Temperature  by  Food.  —  In  cold  weather 
we  eat  more.  We  also  eat  more  fat  and  other  heat- 
producing  foods. 

Effect  of  Wet  Clothing.  — In  getting  the  clothing  wet  the 
cooling  effect  is  not  so  much  from  the  temperature  of  the 
water  as  from  the  loss  .of  heat  in  evaporating  the  water 
from  the  clothing ;  and  this  goes  on  for  a  long  time.  Of 
course  it  is  desirable  to  put  on  dry  clothing  as  soon  as 


Excretion.  1 3 1 

possible.  It  is  dangerous  to  sit  down  in  wet  clothing,  even 
on  a  warm  day.  Children  seldom  take  cold  from  wading, 
even  in  cold  water,  if  barefooted ;  but  with  wet  shoes  and 
stockings  they  are  likely  to  take  cold. 

Mechanical  Protection  by  the  Skin.  —  This  is  the  most 
evident  function  of  the  skin.  The  skin  is  tough,  strong, 
and  elastic,  hence  well  fitted  to  cover  the  body  and  yield 
with  every  motion,  yet  protect  the  softer  and  more  delicate 
tissues  beneath  it  from  injury. 

Absorption  by  the  Skin.  —  The  skin  has  slight  power  of 
absorption ;  hence  there  is  some  danger  in  handling  cer- 
tain poisonous  substances.  The  chief  danger,  however,  is 
when  there  are  cracks  or  sores  on  the  hands.  If  one  must 
handle  suspicious  material,  it  is  well  to  rub  the  hands  with 
vaseline.  To  use  rubber  gloves  is  safer  still. 

Review  of  the  Functions  of  the  Skin.  —  (The  skin  as  a 
sense  organ  will  be  considered  later.)  I.  Sensory.  2. 
Heat-regulating.  3.  Absorptive.  4.  Protective.  5.  Ex- 
cretory. It  will  be  easy  to  remember  these  five  functions 
if  it  is  noted  that  their  initials  spell  the  word  s-h-a-p-e. 

Skin-grafting.  —  Sometimes  after  extensive  burns,  or 
other  injury  of  the  skin,  bits  of  skin  are  taken  from  an- 
other part  of  the  body,  or  from  another  person,  and  trans- 
planted to  the  injured  part,  where  they  grow. 

External  Features  of  the  Kidneys.  —  The  kidneys  are  a 
pair  of  bean-shaped  bodies  attached  to  the  dorsal  wall  of 
the  abdomen.  (See  Fig.  32.)  The  spot  corresponding  to 
the  stem-scar  of  the  bean  is  called  the  kilum.  At  this  point 
are  three  tubes,  the  artery  by  which  blood  enters  the  kid- 
ney, the  vein  by  which  the  blood  leaves,  and  the  ureter,  by 
which  the  urine  is  conveyed  to  the  bladder. 


132  Physiology. 

The  Blood-supply  of  the  Kidneys.  —  On  entering  the 
kidney  the  renal  artery  divides  and  subdivides,  forming  a 
very  complicated  set  of  capillaries.  Through  the  thin  walls 
of  the  capillaries  certain  waste  matters  pass  into  the  cavity 
of  the  kidney,  from  which  they  are  conveyed  by  the  ureter 
to  the  bladder.  (See  Fig.  32.) 

Urea.  —  Urea  is  the  nitrogen-containing  waste  of  the 
body.  There  is  nitrogen  in  muscle,  brain,  and  in  all  the 
important  organs  of  the  body.  When  they  work,  some 
urea  is  formed.  If  the  urea  accumulates  in  the  blood,  it 
acts  as  a  poison  to  the  tissues. 

Importance  of  the  Work  of  the  Kidneys.  —  The  kidneys 
are  the  only  organs  that  can  remove  the  urea  from  the 
blood ;  hence  their  great  importance.  Small  as  they  are, 
their  removal  would  soon  cause  death.  Urea  is  a  solid,  and 
could  not  very  well  be  carried  out  of  the  body  unless  dis- 
solved. So  the  urine  consists  mainly  of  water  containing 
urea,  salt,  and  various  other  substances  in  small  amounts. 

Relation  between  the  Kidneys  and  the  Skin.  —  There  is  a 
very  close  relation  between  the  kidneys  and  the  skin.  In 
warm  weather,  and  when  exercising  actively,  we  sweat  more 
and  the  kidneys  excrete  less  water ;  on  the  other  hand, 
when  we  exercise  less,  and  especially  in  a  cool  place,  we 
sweat  less,  and  the  amount  excreted  by  the  kidneys  is  in- 
creased. For  instance,  when  one  has  a  cold  he  is 
more  or  less  feverish  ;  that  is,  the  action  of  the  skin  is  inter- 
fered with,  and  there  is  less  perspiration.  At  such  time 
the  kidneys  have  more  work  to  do,  and  may  be  so  over- 
worked as  to  injure  them  permanently. 

Summary.  —  i.    When  the  body  works  it  produces  waste  matter. 

2.  Waste  matter  must  be  removed  or  it  will  poison  the  body. 

3.  The  skin  throws  off  sweat,  —  mostly  water  carrying  waste  matter. 


Excretion.  133 

4.  Sweat  is  taken  from  the  lymph  by  the  sweat  glands,  which  are 
coiled  tubes,  opening  on  the  surface  of  the  skin. 

5.  The  skin  consists  of  two  layers,  the  dermis  and  the  epidermis. 

6.  The  amount  of  sweat  varies  with  heat,  exercise,  food,  etc. 

7.  The  body  gives  off  heat  by  (i)  radiation,  (2)  conduction,  (3)  con- 
vection, (4)  evaporation. 

8.  The  temperature  of  the  body  in  health  stays  at  about  98.5°  F. 

9.  The  temperature  is  regulated  by  the  evaporation  of  sweat. 
10.    Heat  is  distributed  through  the  body  by  the  blood. 

u.    In  cold  weather  we  eat  more  fat,  and  other  food,  to  make  heat. 

12.  The  skin  has  five  functions:  touch,  heat-regulation,  absorption, 
protection,  excretion. 

13.  The  kidneys  remove  urea  from  the  blood.     Urea  is  the  nitrogen- 
containing  waste  of  the  body. 

14.  If  much  urea  is  in  the  blood,  the  body  is  poisoned,  and  the  re- 
moval of  the  kidneys  would  soon  cause  death. 

Questions.  —  i.   Do  dogs,  cats,  and  cows  sweat? 

2.  Why  is  thirst  relieved  by  moistening  the  skin? 

3.  Why  is  it  a  good  sign  when  the  skin  of  a  feverish  person  becomes 
moist  ? 

4.  Why  should  clothing  worn  during  the  day  be  removed  at  night  ? 

5.  Can  food,  medicine,  or  poison  be  absorbed  through  the  skin? 


CHAPTER  XIV. 
FOODS  AND  COOKING. 

Necessity  of  Food.  —  Thus  far  we  have  been  studying 
processes  by  which  the  body's  weight  is  reduced.  We 
have  studied  the  oxidation  in  the  tissues  and  the  removal 
of  the  wastes.  Unless  the  tissues  receive  a  supply  of  new 
material,  the  heat  and  energy  of  the  body  cannot  long  be 
kept  up. 

Food  Defined.  —  Foods  are  substances  that  build  tissues 
or  produce  energy  without  injuring  any  organ  or  function 
of  the  body.  Certain  substances  that  do  not  become  part 
of  any  tissues,  nor  in  themselves  produce  energy,  are  use- 
ful in  aiding  the  processes  going  on  in  the  body.  These 
may  be  called  accessory  foods,  e.g.  condiments,  such  as 
pepper. 

Foods  and  Foodstuffs.  —  Most  of  our  articles  of  food 
consist  of  two  or  more  different  kinds  of  materials.  For 
instance,  milk  consists  (i)  chiefly  of  water;  and  in  it  are 
(2)  the  substance  that  makes  cheese  (casein);  (3)  cream, 
from  which  we  get  butter  (fat);  (4)  sugar,  which  gives 
milk  a  sweet  taste;  (5)  salts,  such  as  common  salt,  lime 
salts,  etc.  These  different  materials  are  foodstuffs.  We 
have  many  kinds  of  foods,  but  few  foodstuffs,  which  we 
find  occurring  over  and  over  again,  in  various  forms,  in 
the  numerous  things  we  eat. 


Foods  and  Cooking.  135 

Kinds  of  Foodstuffs.  —  i.    Proteids  (example,  casein). 

2.  Fats.  4.  Water. 

3.  Carbohydrates  (starch  and  sugar).  5.    Salts. 

The  Proteids.  —  The  chief  substance  in  the  white  of  an 
egg  is  albumen,  a  typical  proteid.  Of  the  many  proteids 
some  of  the  more  commonly  known  are  casein  (the  curd 
of  milk),  gluten  (in  grains),  legumin  (in  peas  and  beans), 
fibrin  (in  blood),  myosin  (in  muscles).  Gelatin  (obtained 
from  connective  tissue  and  bones  by  prolonged  boiling) 
differs  considerably  from  the  proteids  in  composition,  but 
may  be  counted  in  with  them.  It  is  less  valuable  as  a  food 
than  the  true  proteids,  although  in  certain  circumstances 
more  desirable  from  the  fact  that  it  is  very  easily  digested. 

Importance  of  Proteids.  —  The  proteids  are  of  special 
importance  as  foods  because  the  most  active  tissues  — 
those  of  the  muscles,  nerves,  and  glands  —  and  the  most 
important  liquids  of  the  body,  e.g.  blood  and  lymph,  con- 
tain proteid.  Proteid  food,  therefore,  must  be  taken  to 
make  good  the  losses  of  these  tissues  during  their  oxida- 
tions. Proteid  is  the  only  foodstuff  containing  nitrogen. 

Proteid-containing  Foods. — The  principal  proteid-contain- 
ing  foods  are  lean  meat,  fish,  eggs,  milk,  cheese,  and  some 
seeds  which  abound  in  the  vegetable  proteids. 

Meat.  —  Lean  meat  has  about  twenty  per  cent  of  proteid, 
the  rest  being  chiefly  water.  Beef  and  mutton  are  more 
easily  digested  than  veal  and  pork.  Pork  sometimes  con- 
tains a  parasitic  worm  called  trichina,  which  causes  illness, 
or  even  death,  if  eaten.  Pork  should  be  thoroughly  cooked 
so  as  to  kill  the  trichinas. 

Fish.  — Fish,  when  fresh,  is  a  good  food.  Although,  as 
a  rule,  salted  meats  are  less  easily  digested  than  fresh, 


136  Physiology. 

salted  codfish  is  a  nourishing  and  economical  food.  Fish 
is  not  an  especially  valuable  brain  food,  as  commonly 
believed. 

Eggs.  —  Eggs  contain  considerable  proteid,  but  their  value 
as  food  has  been  overrated.  The  yolk  has  a  large  amount 
of  fat.  Although  the  egg  has  all  the  material  needed  to 
form  a  chick,  it  is  not  a  perfect  food  for  man. 

Milk.  —  Milk,  as  we  have  seen,  is  an  ideal  food,  in  that 
it  contains  all  the  kinds  of  foodstuffs,  and  in  the  right  pro- 
portion for  the  young  mammal.  But  the  proportions  are 
not  right  for  the  adult.  An  adult  would  need  four  quarts 
and  a  half  daily,  and  then  he  would  not  get  enough  carbo- 
hydrates (represented  in  milk  by  the  sugar).  The  oily 
material  in  milk  is  in  the  form  of  minute  globules,  which 
can  easily  be  seen  under  the  microscope.  Each  of  these 
oil  droplets  is  surrounded  by  a  thin  envelope  of  albumen, 
by  means  of  which  it  is  enabled  to  remain  suspended  for 
some  time  instead  of  rising  quickly  to  the  surface.  Such  a 
mixture  of  oil  in  a  liquid  is  called  an  emulsion.  When 
cream  is  churned  the  albuminous  covering  is  removed  and 
the  butter  " gathers." 

Cheese.  —  Cheese  is  very  rich  in  prcteid,  much  more  so 
than  lean  meat.  Yet,  as  it  is  hard  to  digest,  we  do  not  use 
it  much  as  food ;  we  regard  it  more  as  a  luxury,  while  in 
many  parts  of  Europe  it  is  largely  used  as  food,  taking  the 
place  of  meat.  It  is  a  cheap  food,  and  might  well  be  used 
more  extensively,  especially  by  laboring  men.  When  taken 
with  milk,  it  is  said  to  be  more  readily  digested. 

Vegetable  Proteids.  —  Peas  and  beans  (dried)  contain  as 
much  proteid  (legumin)  as  meat,  and  all  the  cereals  contain 
some  proteid  (gluten). 


Foods  and  Cooking.  137 

Fats.  —  Fats  are  composed  of  carbon,  hydrogen,  and 
oxygen.  The  oxygen  is  small  in  amount,  so  these  foods 
yield  a  great  amount  of  energy  by  the  oxidation  of  their 
carbon  (forming  carbon  dioxid)  and  hydrogen  (forming 
water).  The  fats  most  used  are  animal  fats,  including 
butter.  But  some  vegetable  oils,  such  as  olive  and  cotton- 
seed oils,  are  used. 

The  Carbohydrates.  —  Starch  and  sugar  are  the  chief 
carbohydrates.  They  are  composed  of  carbon,  hydrogen, 
and  oxygen,  but  not  in  the  same  proportions  as  in  fats. 
Starch  is  used  in  larger  quantity  than  any  other  foodstuff 
except  water.  Sugar  is  usually  regarded  as  a  luxury,  yet 
it  is  an  important  food.  It  is  quickly  absorbed. 

Carbohydrate-containing  Foods. — The  principal  carbo- 
hydrate-containing foods  are  the  grains,  vegetables,  and 
fruits.  The  most  important  grains  are  wheat,  corn,  rice, 
oats,  rye,  and  barley. 

Wheat — Wheat  furnishes  the  principal  breadstuff  among 
the  more  civilized  nations.  It  is  especially  adapted  to  the 
temperate  zones.  Taking  into  consideration  its  composi- 
tion, digestibility,  and  other  characteristics,  it  is  the  most 
desirable  of  all  the  grains. 

Wheat  Flour.  —  In  ordinary  white  flour  nearly  all  the 
gluten  has  been  removed  with  the  bran  or  "middlings." 
While  wheat  or  bread  made  from  the  whole  grain  of  the 
wheat  may  support  life,  one  would  starve  if  he  tried  to  live 
on  common  white  bread  alone.  It  is  almost  entirely  starch. 
In  the  "entire  wheat  flour"  it  is«claimed  that  all  the  gluten 
is  retained,  only  the  very  thin  outer  husk  of  the  grain  being 
removed.  It  does  not  make  so  white  a  flour,  but  it  is  better 
adapted  to  use  as  a  food.  If  we  use  white  bread,  having 
thrown  away  the  nitrogenous  part  of  the  wheat,  we  need  to 

10— PHY 


1 3  8  Physiology. 

take  more  proteid  from  other  sources  than  if  we  used  the 
entire  wheat  flour.  This  is  not  economy.  It  is  claimed 
that  the  entire  wheat  bread  is  more  wholesome  as  well  as 
more  nutritious.  The  part  thrown  away  has  in  it  phos- 
phates as  well  as  the  nitrogenous  material.  This  flour  is 
ground  fine  so  that  it  has  not  the  coarse  particles  which  are 
in  Graham  flour,  and  which  are,  in  some  persons,  a  source 
of  irritation  to  the  mucous  coat  of  the  digestive  tube. 

Corn.  —  Corn  is  one  of  the  most  nutritious  of  the  grains. 
Although  somewhat  less  readily  digested  than  similar 
preparations  of  wheat,  and,  consequently,  less  desirable 
for  indoor  workers,  it  is  a  fact  that,  for  a  given  amount  of 
money,  more  nutriment  can  be  obtained  in  corn  meal  than 
in  any  other  food  known. 

Rice.  —  Rice  forms  a  larger  part  of  human  food  than  the 
product  of  any  other  plant,  being  often  an  almost  exclusive 
diet  in  India,  China,  and  the  Malayan  islands.  Rice  has  a 
larger  proportion  of  starch,  and  less  of  fats  and  proteids, 
than  the  other^rains.  It  is  best  adapted  for  the  food  of 
warm  climates. 

Oats.  —  This  grain  was  first  used  as  food  for  man  by  the 
Scotch,  but  the  use  has  extended  and  become  prevalent  in 
this  country.  In  point  of  nutrition  it  is  ranked  higher  by 
some  than  ordinary  grades  of  wheat  flour. 

Rye.  —  Rye  grows  farther  north  than  other  grains,  and 
is  largely  used  for  bread  in  Russia  and  parts  of  Germany. 
It  is  a  valuable  food,  though  less  nutritious  and  less  digest- 
ible than  the  corresponding  preparations  of  wheat. 

Barley.  —  This  grain  has  wide  range  of  cultivation,  and, 
while  inferior  to  wheat,  is  considerably  used  where  other 
grains  cannot  be  raised. 


Foods  and  Cooking.  139 

Potatoes.  —  Potatoes  contain  about  twenty  per  cent  starch, 
two  per  cent  of  proteid,  and  no  fat,  the  remainder  being 
chiefly  water,  with  some  useful  salts,  especially  potash  salts. 
In  spite  of  its  relatively  low  food  value,  the  potato  is  our 
most  useful  vegetable  on  account  of  its  abundance,  the  ease 
with  which  it  can  be  preserved,  and  the  readiness  and  the 
variety  of  ways  in  which  it  can  be  cooked. 

Other  Vegetables.  —  The  chief  nutrient  in  vegetables  is 
starch,  though  in  many  the  starch  is  present  in  small  amounts. 
The  salts  and  acids  present  are  of  value,  and  care  should 
be  observed  not  to  remove  too  much  of  these  salts  in  cook- 
ing. The  fibrous  matter,  cellulose,  while  indigestible,  is  of 
value  in  adding  bulk  to  the  mass  of  food  to  be  digested. 

Scurvy.  —  Formerly  sailors  were  subject  to  scurvy ;  this 
is  now  attributed  to  a  diet  of  fat  and  salt  meat,  to  the 
exclusion  of  fresh  vegetables,  etc.  The  disease  is  avoided 
by  a  greater  use  of  vegetables,  lime  juice,  etc. 

Fruits.  —  Many  of  the  fruits,  such  as  bananas  and 
apples,  have  considerable  starch  and  sugar.  But  the 
fruits  are  more  useful  to  us  on  account  of  their  flavor, 
due  to  aromatic  bodies,  and  to  their  salts  and  the  peculiar 
fruit  acids. 

Water.  —  Water  constitutes  about  two  thirds  of  the 
entire  weight  of  the  body.  It  constitutes  the  bulk  of  the 
liquids  we  have  studied,  blood,  lymph,  sweat,  saliva,  bile, 
etc.  Water  dissolves  and  carries  all  the  material  of  the 
body.  Hence  we  need  a  large  Amount  of  it ;  of  course  we 
must  remember  that  we  get  a  good  deal  of  water  in  most 
of  our  solid  foods. 

Rain  Water. —Water,  as  it  comes  from  the  clouds,  is 
pure.  After  enough  rain  has  fallen  to  wash  the  air,  rain 


140  Physiology. 

water  is  pure,  and  if  caught  on  a  clean  roof  (especially  a 
slate  roof)  and  kept  in  a  clean  cistern,  it  is  good  drinking- 
water. 

Well  Water.  —  Falling  upon  the  earth,  the  rain  water 
niters  down  until  stopped  by  some  layer,  such  as  clay, 
through  which  it  cannot  soak.  This  water  is  the  supply 
of  our  wells  and  springs.  It  always  has  more  or  less 
earthy  matter,  especially  lime,  in  solution,  and  is  therefore 
more  or  less  "  hard."  Unless  a  large  amount  of  mineral 
matter  or  some  special  material  is  dissolved  in  it,  it  is 
ordinarily  good  drinking-water.  Such  water  is  not  pure, 
in  the  strict  sense  of  the  word,  but  is  pure  for  drinking 
purposes. 

Impurities  in  Water.  —  The  great  source  of  danger  is 
from  what  are  called  "organic"  impurities.  Bacteria  do 
not  thrive  in  pure  water.  They  must  have  something  on 
which  to  feed  and  grow.  But  in  water  containing  a  large 
amount  of  decaying  animal  or  vegetable  matter  they  are 
likely  to  abound.  And  the  most  dangerous  sources  of 
contamination  are  cesspools  and  sewers.  Water  may  be 
contaminated  by  such  material  and  not  have  bacteria  in 
it,  but  is  very  likely  to  harbor  such  foes. 

Contamination  from  Cesspools.  —  The  ordinary  cesspool 
is  a  grave  source  of  danger.  Because  the  well  may  be  on 
higher  ground  than  the  cesspool  does  not  give  assurance 
that  the  water  may  not  be  polluted.  Often  when  the  sur- 
face of  the  ground  slopes  in  one  direction,  the  strata 
underneath  may  slope  in  the  opposite  direction,  and  the 
well  may  be  the  reservoir  into  which  the  cesspool  is 
drained.  Good  authorities  say  that  a  cesspool  should  not 
be  allowed  within  a  hundred  feet  of  a  well. 


Foods  and  Cooking.  141 

Abolish  the  Cesspool.  —  It  is  better  and  safer  to  have 
no  cesspool.  Where  a  sewer  system  is  not  to  be  had,  it  is 
better  to  allow  no  great  accumulation  of  such  material.  A 
deep  pit  in  which  a  quantity  of  semiliquid  matter  gathers 
is  not  only  a  nuisance  but  a  source  of  danger.  Privies 
should  have  a  very  shallow  pit,  or  none,  and  should  be 
cleaned  often.  There  should  be  a  little  dust  sprinkled  in 
each  day,  and  occasionally  some  chlorid  of  lime  or  sulphate 
of  iron. 

Typhoid  Fever.  —  Typhoid  fever  is  usually  caused  by 
drinking-water.  The  excretions  of  some  one  who  has  had 
the  disease  find  their  way  into  the  source  of  the  drinking- 
water.  In  many  cases  this  has  been  clearly  proved.  Of 
course  the  excretions  of  all  such  patients  should  be  either 
destroyed  or  thoroughly  disinfected. 

Ice  Water.  —  Although  bacteria  will  not  develop  in  a 
cold  place,  they  are  not  killed  when  frozen  in  ice,  as 
was  formerly  supposed.  Further,  ice,  in  forming,  does 
not  throw  out  all  the  impurities,  as  was  formerly  believed. 
So  it  is  not  safe  to  drink  water  formed  from  melted  ice 
unless  the  water  of  which  that  ice  was  made  was  good 
water.  The  ice  taken  from  ponds  is  not  safe.  If  ice  is 
made  artificially  from  suitable  drinking-water,  the  melted 
product  will  be  essentially  unchanged  so  far  as  the  com- 
position is  concerned.  Water  may  be  cooled  by  placing 
any  ice  around  it,  and  we  may  have  the  desired  tempera- 
ture without  danger. 

Boiling  Water.  —  When  one  cannot  get  good  drinking- 
water,  or  when  away  from  home  where  the  water  is  of 
doubtful  purity,  it  is  better  to  boil  the  water  before  using 
it,  either  as  a  drink  or  in  preparations  of  food  that  are  not 
to  be  thoroughly  cooked.  It  seems  to  be  proved  that  it  is 


142  Physiology. 

better  to  heat  the  water  twice  nearly  to  the  boiling  point 
than  to  boil  once  only.  The  first  heating  may  start  the 
germs  into  more  active  life,  causing  them  to  sprout  (so  to 
speak),  and  a  second  heating  several  hours  later  may  easily 
kill  them ;  whereas  it  has  been  proved  that  one  hard 
boiling  will  not  always  kill  the  germs. 

Cautions  as  to  Drinking-water.  —  If  one  uses  tea  and 
coffee,  it  is  safer  to  content  one's  self  with  these,  and  not 
drink  much  water  till  that  which  is  safe,  as  from  deep 
wells,  can  be  obtained.  In  hot  weather,  and  especially 
for  those  who  are  engaged  in  hard  work,  it  has  been 
found  that  a  little  oatmeal  stirred  in  the  water  is  bene- 
ficial. When  overheated,  avoid  drinking  much  cold  water. 
Repeatedly  rinse  the  mouth  with  cool  water,  and  swallow 
very  little.  This  is  the  way  trainers  manage  a  horse  at  a 
race,  and  it  is  sensible  to  treat  a  man  as  carefully. 

Salts.  —  Salts  include  many  substances  besides  common 
salt.  They  aid  in  the  solution  of  various  substances  dur- 
ing digestion  and  in  other  processes.  We  cannot  live 
without  them.  Lime  in  the  form  of  calcium  phosphate  and 
calcium  carbonate  is  essential,  especially  in  the  bones  and 
teeth. 

Necessity  of  a  Mixed  Diet.  —  Our  experience,  together 
with  the  results  of  experiments  on  animals,  teaches  that 
we  could  not  live  long  if  fed  on  any  one  class  of  food- 
stuffs alone.  We  must  take  a  representative  of  each  of 
the  groups.  We  have  noticed  that  most  of  our  foods 
already  contain  more  than  one  foodstuff.  We  so  combine 
them  as  to  get  suitable  proportions.  Thus  we  eat  bread 
and  butter  (a  small  amount  of  fat  with  a  large  quantity  of 
starch  and  a  little  gluten),  meat  and  potato,  crackers  and 
cheese,  pork  and  beans,  egg  on  toast,  bread  and  milk,  rice 


Foods  and  Cooking.  143 

and  fowl,  macaroni  and  cheese ;  they  "  go  well  together  " 
chiefly  because  each  contains  what  the  other  lacks. 

Disadvantages  of  a  One-sided  Diet.  —  In  order  to  get 
enough  nitrogen  from  bread  alone,  one  would  have  to  eat 
about  four  pounds  a  day ;  meanwhile  twice  as  much  car- 
bon as  is  needed  would  be  taken,  thus  throwing  an  undue 
amount  of  work  upon  the  digestive  organs.  Again,  one 
would  need  to  consume  about  six  pounds  of  meat  to  get 
the  requisite  amount  of  carbon,  and  six  times  as  much 
nitrogen  as  is  needed  would  be  taken ;  to  get  rid  of  this 
extra  nitrogen  would  severely  tax  the  kidneys  and  liver. 

Effect  of  Cold  on  Appetite  for  Fats.  —  In  cold  climates 
a  large  amount  of  fat  is  consumed,  while  in  the  tropics 
starch  is  the  chief  food.  Our  appetites  call  for  more  of 
the  fatty  foods  during  the  winter  season. 

Proper  Diet — While  common  experience  has  led  people 
to  adopt  a  mixed  diet,  the  proportions  of  the  different  food- 
stuffs is  not  always  what  it  should  be.  The  proportions 
of  the  foodstuffs  (exclusive  of  water)  may  be  roughly  stated 
as  about  I  part  of  proteid,  I  part  of  fat,  3  parts  of  carbo- 
hydrates. But  this  will  vary  somewhat  with  the  amount 
of  work  done,  and  other  varying  conditions. 

Vegetarians.  —  The  so-called  "  vegetarians  "  recognize 
the  need  of  proteid  food,  and  most  of  them  seek  proteid  in 
eggs,  milk,  and  cheese.  But  these  are  animal  products, 
and  the  name  "vegetarian"  is  inconsistent.  They  are 
merely  "  anti-meat  eaters."  That  we  are  adapted  for 
using  flesh  as  part  of  our  food  is  indicated  in  at  least  two 
anatomical  features :  (i)  we  have  canine  teeth,  though  not 
so  fully  developed  as  in  the  carnivora ;  (2)  the  intestine  in 
carnivora  is  very  short,  that  of  the  herbivora  very  long, 


144  Physiology. 

but  in  man  intermediate.     Nevertheless,  it  is  undoubtedly 
true  that  many  persons  eat  too  much  meat. 

Beef  Tea.  —  Beef  tea  and  various  beef  extracts  are  help- 
ful. There  is  not  enough  nourishment  in  them  to  maintain 
strength  without  other  food.  But  many  of  the  soups  and 
drinks  made  from  them  are  beneficial.  They  refresh  the 
tired  system  wonderfully.  If  the  man  who  feels  "  fagged 
out"  and  takes  a  drink  of  liquor  to  "brace  him  up,"  as  he 
says,  were  to  take  a  cup  of  hot  bouillon,  he  would  find  him- 
self "braced  up,"  for  the  time,  without  any  bad  reaction, 
or  permanent  injury  to  the  system. 

Cooking.  —  Cooking  is  designed  to  make  food  more  pala- 
table and  more  digestible.  Some  foods,  such  as  eggs,  are 
as  digestible  before  they  are  cooked  as  after.  But  many 
foods  in  the  raw  state  are  unattractive,  whereas  cooking 
usually  develops  an  agreeable  odor  and  taste.  Cooking 
should  soften  the  harder  and  tougher  tissues,  such  as  cellu- 
lose in  vegetables  and  the  connective  tissue  of  animal  foods. 
Cooking  starch  causes  the  starch  grains  to  swell  and  burst, 
and  makes  the  starch  more  digestible. 

Making  Soup. — -If  meat  be  cut  into  small  pieces  and  put 
into  cold  water,  and  the  water  gradually  warmed,  the  solu- 
ble material  of  the  meat  may  be  extracted,  and  this  is  the 
principle  followed  in  making  soups. 

Boiling  Meat.  —  If  we  wish  to  cook  the  meat  itself,  the 
juices  should  be  retained  instead  of  withdrawn.  For  this 
purpose  boiling  water  is  poured  over  the  meat  to  coagulate 
the  outer  layer  and  prevent  the  extraction  of  the  juices. 

Baking,  Roasting,  and  Broiling.  —  The  same  principle 
applies  to  baking,  roasting,  and  broiling.  The  outside  is 
subjected  to  high  heat  at  the  beginning  of  the  cooking, 
which  forms  a  sort  of  crust  through  which  the  nutritious 


Foods  and  Cooking.  145 

juices  cannot  escape.  In  these  modes  of  cooking  it  is  very 
desirable  to  reduce  the  heat  after  the  first  few  minutes,  so 
that  the  interior  may  be  cooked  enough  without  over-cook- 
ing the  outside ;  this  is  especially  true  in  broiling. 

Frying.  —  Frying,  as  ordinarily  done,  is  not  a  good  mode 
of  cooking ;  in  fact,  is  often  very  bad,  as  the  food  is  fre- 
quently soaked  with  fat  and  rendered  indigestible.  But 
true  frying,  that  is,  by  immersion  in  boiling  fat,  is  a  good 
mode  of  cooking.  This  coagulates  the  albuminous  sub- 
stance on  the  outside,  keeps  in  the  nutritious  juices,  and 
prevents  soaking  with  the  fat. 

Summary.  —  I .    Food  is  to  build  tissue  or  produce  energy. 

2.  Foodstuffs  are  the  simpler  materials  in  foods. 

3.  The  foodstuffs  are  proteids,  fats,  carbohydrates,  water,  salts. 

4.  The  proteids  are  albumen,  casein,  gluten,  legumin,  fibrin,  myosin, 
gelatin. 

5.  They  are  found  in  meat,  egg,  milk,  peas,  beans,  and  a  little  in  grains. 

6.  The  carbohydrates  include  starch  and  sugar. 

7.  Starch  is  obtained  from  potatoes  and  the  grains. 

8.  The  most  important  grains  are  wheat,  oats,  corn,  rice,  and  rye. 

9.  Wheat  is  considered  the  best  grain,  though  more  nourishment 
can  be  obtained  from  corn  meal,  for  a  given  amount  of  money,  than  from 
any  other  food. 

10.  Vegetables  contain  some  starch,  but  are  of  value  from  giving 
bulk  to  the  food. 

1 1 .  Water  containing  decaying  organic  matter  is  dangerous  to  drink, 
because  it  is  likely  to  contain  bacteria,  which  poison  us  or  cause  disease. 

12.  Boiling  water  usually  kills  the  bacteria  in  it. 

13.  Drinking  ice  water  is  injurious. 

14.  We  take  a  mixed  diet,  as  no  one  food  contains  all  we  need. 

15.  Cooking  is  to  render  food  more  palatable  and  digestible. 

Questions.  —  i.    Is  the  appetite  always  a  safe  guide  in  eating? 

2.  Which  kind  of  foodstuff  is  most  expensive?     Why? 

3.  Why  is  bread  the  "  staff  of  life  "  ? 

4.  Make  a  list  of  the  common  foods,  naming  the  foodstuffs  in  them. 

5.  How  do  flour  and  potatoes  compare  in  cheapness  ? 


CHAPTER   XV. 
THE   DIGESTIVE  SYSTEM. 

DIGESTION   IN  THE   MOUTH. 

The  Object  of  Food.  —  The  tissues  are  worn  out  by  their 
oxidation.  They  are  built  up  again  by  the  blood,  and  the 
blood  is  renewed  by  the  food. 

The  Digestive  Tube.  —  All  food  must  be  reduced  to  the 
liquid  condition,  if  it  is  not  already  liquid.  The  chief  organ 
in  this  work  of  liquefying  the  food  is  the  digestive  tube,  or 
"  alimentary  canal."  As  the  food  passes  through  the 
digestive  tube  it  is  ground  and  liquids  are  poured  upon  it. 
Thus  it  is  reduced  to  a  liquid  that  can  be  absorbed  and 
taken  into  the  blood. 

The  Work  of  the  Digestive  Tube.  —  To  take  a  special 
instance,  a  muscle  is  in  part  worn  out  by  the  oxidation 
during  its  activity ;  to  replace  the  loss  suppose  we  take  a 
piece  of  steak.  We  cannot  substitute  this  directly  in  the 
place  of  the  worn-out  tissue.  In  digesting  the  steak  we 
must  tear  it  to  pieces,  and  reduce  it  to  a  liquid  form  by  the 
action  of  the  teeth  and  by  the  various  liquids  from  the 
glands  along  the  digestive  tube.  The  beefsteak,  as  such, 
must  be  thoroughly  destroyed ;  in  the  liquid  produced  by 
the  digestion  of  the  beef  there  is  no  trace  whatever  of  the 
structure  of  the  beef.  But  the  blood,  taking  this  material, 
builds  muscle  which  can  hardly  be  distinguished  from  the 
original  beef. 

146 


The  Digestive  System.  147 

If  the  food  taken  is  a  liquid  and  ready  to  build  tissue,  as 
a  thin  syrup,  it  will  not  need  to  go  through  these  changes. 

The  Organs  of  Digestion.  —  The  organs  of  digestion  are 
the  digestive  tube,  with  the  masticating  organs,  and  the 
glands  in  and  along  the  walls  of  the  tube. 

The  parts  of  the  digestive,  tube  are  the  mouth,  the 
pharynx,  the  gullet  (or  esophagus),  the  stomach,  the  small 
intestine,  and  the  large  intestine. 

The  Mouth  and  Gullet.  —  At  the  back  of  the  mouth  may 
be  seen  the  soft  palate  with  the  cylindrical  uvula  hanging 
from  its  center.  Beyond  this  is  the  cavity  of  the  pharynx, 
which  narrows  below  into  the  gullet,  a  red-walled,  muscular 
tube,  extending  along  the  back  side  of  the  windpipe,  and 
close  to  the  spinal  column.  It  extends  the  length  of  the 
chest,  and  then  passes  through  the  diaphragm  and  widens 
into  the  stomach,  at  the  upper  left  end  of  the  latter. 

The  Stomach.  —  The  stomach  is  somewhat  pear-shaped, 
with  the  larger  end  to  the  left.  At  the  right  end  it  tapers 
into  the  small  intestine,  the  first  foot  or  so  of  which  is 
called  the  duodenum.  (See  Figs.  53,  72,  and  74.) 

The  Liver  and  Pancreas.  —  Just  below  the  diaphragm  is 
the  dark-colored  liver,  overlapping  a  large  portion  of  the 
stomach.  Between  two  of  the  three  lobes  of  the  liver  is  the 
bile  sac,  whose  duct  enters  the  duodenum  a  short  distance 
from  the  stomach.  The  pancreas  is  a  pinkish  organ  of 
irregular  shape  lying  along  the  stomach  and  duodenum. 
Its  duct  enters  the  duodenum  at  the  same  point  as  the  bile 
duct. 

The  Intestine.  —  The  first  part  of  the  intestine  is  the 
small  intestine.  At  the  lower  right  part  of  the  abdomen 


148 


Physiology. 


this   enters  the  larger  intestine.      The  intestine  is  held 
in   place    by  the   mesentery,   a  thin   fold  of   transparent 

membrane  folded  closely 
around  it,  and  supported 
from  the  back  wall  of 
the  abdominal  cavity. 
Between  the  two  layers 
of  the  mesentery  are  the 
branches  of  the  artery 
supplying  the  walls  of 
the  intestines,  and  the 
veins  that  convey  the  ab- 
sorbed food  from  the 


intestine  to  the  liver. 


Fig.  66.     Cross-section  of  Abdomen. 


The  Mouth.  -—  The 
pupil  should  carefully  examine  his  own  mouth  by  means 
of  a  mirror.  We  are  apt  to  think  of  the  mouth  as  a  cavity 
of  considerable  size,  as  indeed  it  is  when  fully  opened; 
but  we  are  not  so  likely  to  think  how  completely  the  cavity 
disappears  when  the  mouth  is  closed.  If  one  notes  the 
sensations  from  the  mouth  when  it  is  closed,  he  will  per- 
ceive that  the  tongue  almost  entirely  fills  the  space,  touch- 
ing the  roof  of  the  mouth,  and  the  teeth  in  front  and  at 
the  sides. 

The  Tongue. — The  tongue  consists  chiefly  of  muscles, 
running  in  different  directions,  thus  giving  it  a  variety  of 
motions.  The  tongue  is  the  chief  organ  of  taste,  and  is 
therefore  (with  the  sense  of  smell)  the  gate-keeper  of  the 
digestive  tube.  The  tongue  has  also  a  keen  sense  of 
touch,  and  so  is  useful  in  detecting  and  removing  any 
food  particles  that  may  remain  on  the  teeth  after  eating, 
During  mastication  the  tongue,  with  the  lips  and  cheeks, 


The  Digestive  System. 


149 


keep  the  food  between  the  teeth.  When  the  morsel  of 
food  is  sufficiently  masticated,  the  tongue  pushes  it  back 
into  the  pharynx  to  be  swallowed. 

The  Teeth.  —  The  teacher  can  usually  obtain  a  supply  of  teeth  from 
the  dentist  for  the  asking.  These  should  be  cleaned  before  using  them 
in  the  class.  Use  pearline  or  any  washing  soda.  Let  each  pupil  make 
a  drawing  of  one  of  each  of  the  four  kinds  of  teeth  ;  draw  both  a  front 
(outer  surface)  and  a  side  view  (surface  adjacent  to  another  tooth)  of 
all  but  a  molar. 


Longitudinal  Section 


Side  View 


Face  View 


Enamel 

Pulp  Cavity 

Dentine 

Cement 


Crown 


Neck 


Root 


Hole  for  Blood  Tubes  and  Nerves J 

Fig.  67.    Parts  of  a  Tooth.     (Incisor.) 


External  Features  of  a  Tooth.  —  Examine  one  of  the 
front  teeth.  It  has  the  following  parts  :  — 

1.  The  crown,  the  part  that  is  above  the  gum. 

2.  The  root,  the  part  that  was  buried  beneath  the  gum. 

3.  The  neck,  dividing  the  crown  from  the  root. 

4.  A  hole  at  the  tip  of  the  root. 

To  make  a  Section  of  a  Tooth.  —  Let  each  pupil  prepare  a  longitudi- 
nal section  of  a  tooth  as  follows :  Embed  a  tooth  in  a  little  sealing  wax 
on  the  end  of  a  spool,  cork,  or  block  of  wood.  With  a  grindstone  grind 
away  one  half,  showing  the  pulp  cavity  to  the  tip  of  the  root,  as  in 
Fig.  67.  Make  a  drawing  of  the  surface  thus  exposed,  naming  the 


150  Physiology. 

parts.     If  human  teeth  cannot  be  obtained,  almost  any  kind  will  serve. 
Let  each  pupil  keep  his  preparation. 

Structure  of  a  Tooth.  —  i.  The  pulp  cavity,  communi- 
cating with  a  hole  in  the  tip  of  the  root,  through  which 
the  nerve  and  blood  tube  entered. 

2.  The  bulk  of  the  tooth  is  made  of  a  substance  called 
dentine  (ivory). 

3.  The  crown  of  the  tooth  has  a  covering  of  enamel,  a 
very  hard  substance. 

4.  The  root  is  covered  with  a  bony  substance,  called 
cement. 

The  Arrangement  of  the  Teeth.  —  Beginning  at  the  middle 
of  the  front  of  the  mouth,  there  are  (in  the  normal  adult) 
eight  teeth  in  each  half  jaw :  two  incisors,  one  canine,  two 
bicuspids  (or  premolars),  and  three  molars  (see  Fig.  68). 

Dental  Formula.  —  The  kinds  and  arrangement  of  teeth 
are  expressed  by  a  dental  formula,  in  which  the  nume- 
rators indicate  the  upper  jaw  and  the  denominators  the 
lower,  thus :  If,  C{,  PMf ,  Mf  (for  one  side  of  the  head). 

The  Kinds  of  Teeth.  —  The  crown  of  an  incisor  is  chisel 
shaped ;  but  the  root  is  flattened  in  the  opposite  direction, 
i.e.  at  right  angles  to  the  jaw,  instead  of  parallel  to  it,  as 
in  the  crown.  The  canine  tooth  has  a  conical  crown,  and 
a  longer  root  than  the  incisor.  The  bicuspid  has  two 
points.  The  molar  has  a  cube-shaped  crown,  and  usually 
two  or  three  roots. 

The  Milk  Teeth.  —  The  thirty-two  teeth  of  the  perma- 
nent set  were  preceded  by  a  temporary  set  of  twenty  milk 
teeth.  Because  the  first  set  is  temporary,  it  should  not 
therefore  be  neglected.  Cavities  in  these  should  be  filled 
and  the  teeth  kept  clean.  Before  the  temporary  set  has 


The  Digestive  System. 


gone  the  first  of  the  permanent  set  appear.  The  first  of 
these,  often  called  the  "  six-year  molars,"  are  just  back  of 
the  hindermost  "milk  molars."  These  should  receive 
especial  care,  as  they  will  never  be  replaced.  Any  begin- 
ning of  decay  in  them  ought  to  receive  prompt  attention. 


KINDS   OF   TEETH 
Incisors    - — .... 


Upper 


TIME   OF   APPEARANCE 
7th  Month 
9th      " 

18th      '* 

I2th      " 
24th      " 


TEMPORARY   SET 
Upper 


PERMANENT   SET 
Fig.  68.    TEETH  :   Kinds,  Arrangement,  and  Times  of  Appearance. 

The  Care  of  the  Teeth.  —  The  teeth  need  careful  atten- 
tion. They  should  be  thoroughly  brushed  at  least  twice  a 
day,  on  rising  and  on  going  to  bed.  It  would  be  better  to 
clean  them  after  each  meal  also.  If  a  tooth  powder,  recom- 


152  Physiology. 

mended  by  a  reliable  dentist,  is  not  used,  a  good  white 
castile  soap  will  serve  well.  It  is  better  to  use  tepid  water. 
Toothpicks  are  useful  in  removing  the  larger  particles. 
Quill  toothpicks  are  best ;  metal  should  never  be  used. 
The  teeth  should  be  examined  twice  a  year  by  a  dentist, 
and  any  cavities  promptly  filled. 

Cause  of  Decay  of  Teeth.  —  If  the  teeth  are  not  thoroughly 
cleaned  the  particles  of  food  which  remain  will  soon  begin 
to  decay.  This  decay  is  caused  by  the  growth  of  germs, 
usually  some  kind  of  bacteria,  and  the  decay  thus  begun 
is  likely  to  develop  acids  which  attack  the  limy  material 
of  which  the  teeth  are  composed.  When  it  is  necessary 
to  take  acid  medicines,  care  should  be  taken  not  to  let 
them  come  in  contact  with  the  teeth.  Sweet  substances 
are  very  likely  to  decompose  and  form  acids ;  so  we  must 
clean  the  teeth  after  eating  candies.  When  the  teeth  are 
neglected,  a  limy  substance,  called  tartar,  forms  on  them 
and  encourages  decay. 

The  Salivary  Glands.  —  The  salivary  glands  make  the 
saliva  and  pour  it  into  the  mouth.  There  are  three  pairs 
of  salivary  glands  —  the  parotid,  just  back  of  the  angle  of 
the  jaw,  under  the  ear ;  its  duct  opens  on  the  inside  of  the 
cheek  opposite  the  second  molar  of  the  upper  jaw.  The 
submaxillary  gland  lies  under  the  angle  of  the  jaw ;  its 
duct  opens  under  the  tongue  near  the  front  of  the  mouth. 
The  sublingual  gland  is  in  front  of  the  submaxillary  and 
empties  under  the  tongue  (see  Fig.  74). 

Salivary  Ducts  in  our  Mouths.  —  If  the  inside  of  one's  cheek  be 
examined  by  the  use  of  a  hand  mirror,  the  opening  of  the  duct  from  the 
parotid  gland  may  be  seen  opposite  the  second  molar  of  the  upper  jaw. 
It  usually  looks  like  a  pink  and  white  spot,  resembling  a  wound  of  a 
bee  sting.  Sometimes  saliva  may  be  seen  issuing  from  it. 


The   Digestive  System.  153 

Action  of  the  Salivary  Glands.  —  The  salivary  glands 
pour  into  the  mouth  a  liquid  which  they  make  from 
materials  taken  from  the  blood.  In  structure  the  gland 
may  be  compared  to  a  bunch  of  grapes,  the  grapes  repre- 
senting the  little  cavities,  with  a  wall  of  cells  that  make 
the  saliva.  From  each  of  these  cavities  the  liquid  passes 
into  its  duct,  represented  by  the  stem  of  a  single  grape; 
many  of  these  unite  to  form  the  main  duct,  which  corre- 
sponds to  the  main  stem.  A  thick  network  of  capillaries 

Mucous  Membrane 


Duct  of  Gland 


Secreting  Cells 


Vaso- dilator 

Nerve 


^^ 

Fig.  69.    Diagram  of  a  Salivary  Gland.     (After  Landois  and  Stirling.) 

surrounds  the  gland ;  the  liquid  part  of  the  blood  (plasma) 
soaks  out  through  the  capillary  walls  and  surrounds  the 
gland ;  it  is  now  called  lymph ;  from  the  lymph  the  gland 
directly  obtains  its  material. 

Nerve   Control   of    Salivary  Glands. — The   glands   are 
doubly  dependent  on  nerve  control:  — 

1.  Through  the  nerve  control  of   the  muscles   in  the 
walls  of   the  arteries  the  amount  of   blood  sent   to   the 
glands  is  regulated. 

2.  Nerves  also  go  to  the  cells  of  the  gland  to  control 
their  activity.     When  we  taste,  smell,  see,  or  even  when 
we  think  of,  some  delicious  food  the  mouth  may  "  water," 

1 1 — PHY 


T  54  Physiology. 

as  we  say,  i.e.  the  salivary  glands  are,  by  reflex  action, 
stimulated  to  activity ;  on  the  other  hand,  some  emotions, 
such  as  fear,  check  the  flow  of  saliva. 

Saliva  and  its  Uses.  —  The  saliva  is  mostly  water,  and, 
when  we  are  not  eating,  serves  (i)  to  keep  the  mouth  moist. 
The  water  of  the  saliva  soaks  the  food  during  mastica- 
tion and  (2)  helps  the  process  of  grinding;  it  (3)  enables 
us  to  taste  by  dissolving  any  food  that  is  soluble ;  it 
further  (4)  enables  us  to  swallow  what  would  otherwise 
be  a  dry  powder.  The  special  element  of  the  saliva, 
ptyalin,  has  the  power  (5)  of  changing  starch  to  sugar. 

Amount  of  Saliva.  —  The  amount  of  saliva  secreted 
daily  is  estimated  at  three  pints.  Of  course  the  glands 
should  be  allowed  to  rest  between  meals.  The  habit  of 
chewing  gum,  though  supposed  to  aid  digestion,  undoubt- 
edly does  far  more  harm  than  good.  During  the  resting 
period  the  glands  accumulate  material  for  the  active  work 
of  secretion,  for  there  is  no  sac  in  which  to  store  the 
saliva,  and -it  must  be  made  as  fast  as  is  needed. 

Mucous  Glands  and  Mucus.  —  Besides  the  salivary  glands, 
there  are  great  numbers  of  simple  glands  in  the  mucous 
membrane  lining  the  mouth.  These  secrete  a  clear  sub- 
stance called  mucus,  resembling  white-of-egg.  It  is  mucus 
in  saliva  that  makes  it  "stringy." 

Mumps.  —  In  the  mumps  the  salivary  glands  are  in- 
flamed and  painful.  This  is  most  noticeable  in  the 
parotid  gland,  which  feels  the  pressure  of  the  lower  jaw 
in  the  attempt  to  chew. 

Summary. —  i.  The  chief  work  of  digestion  is  to  make  the  food  into 
a  liquid,  ready  to  be  absorbed  and  become  part  of  the  blood. 

2.  The  digestive  system  consists  of  a  long  tube,  through  which  the 
food  passes,  being  subjected  to  mechanical  and  chemical  processes. 


The   Digestive  System.  155 

3.  The  parts  of  the  digestive  tube  are  the  mouth,  gullet,  stomach, 
and  intestines. 

4.  Along  this  tube  are  several  large  glands,  such  as  the  salivary 
glands,  pancreas,  and  liver,  which  make  liquids  to  pour  upon  the  food. 

5.  The   tongue  is   composed   of  muscles,   is   very  movable,  and 
(i)    tastes   the   food;   (2)   keeps  the  food  between  the  teeth  during 
chewing;  (3)  aids  in  swallowing. 

6.  A  tooth  has  crown,  neck,  and  root. 

7.  The  tooth  consists  of  dentine,  containing  a  pulp  cavity.     The 
crown  is  covered  with  enamel,  and  the  root  is  covered  with  cement. 

8.  There  are  thirty-two  teeth  in  a  full  set,  eight  in  each  half  jaw, 
beginning  at  the  front,  two  incisors,  one  canine,  two  bicuspids,  and 
three  molars.     The  first  set  of  twenty  teeth  are  called  "  milk  teeth." 

9.  The  teeth  must  be  kept  clean  by  brush  and  tooth  powder. 

10.  There  are  three  pairs  of  salivary  glands,  parotid,  submaxillary, 
and  sublingual.     Their  action  is  controlled  by  nerves. 

1 1 .  The  chief  use  of  saliva  is  to  change  starch  to  sugar. 

Questions.  —  i.   Why  should  we  not  crack  nuts  with  the  teeth  ? 

2.  Why  does  the  physician  examine  the  tongue  of  his  patient? 

3.  Is  it  well  to  eat  much  soaked  food ?     Why  not? 

4.  How  many  teeth  have  you,  and  of  what  kinds? 

5.  Why  is  gum-chewing  injurious  ? 


CHAPTER   XVI. 
DIGESTION  IN  THE  STOMACH. 

The  Pharynx.  —  The  cavity  back  of  the  mouth,  beyond 
the  soft  palate,  is  the  pharynx.  The  pharynx  is  a  funnel- 
shaped  cavity,  connecting  above  with  the  passages  from 
the  nostrils;  in  front  it  opens  into  the  mouth;  below  it 


Eustachian  Tube 


Pharynx 
Epiglottis,  Raised 

Gullet,  Closed 
Glottis,  Open 


Fig.  70.   Positions  of  the  Organs  of  the  Mouth  and  Throat  during  Breathing. 

connects  with  the  windpipe,  through  the  glottis,  and  with 
the  gullet,  which  lies  just  back  of  the  windpipe  (see  Figs. 
70  and  71). 

Position  of  Organs  during  Respiration.  —  In  quiet  respira- 
tion the  tongue  nearly  fills  the  mouth.  The  base  of  the 
tongue  is  nearly  covered  by  the  soft  palate,  which  curves 
downward  from  the  hard  palate,  and  by  the  epiglottis  pro- 
jecting upward  from  below.  The  glottis  is  open  and  the 

156 


Digestion  in  the  Stomach.  157 

gullet  is  closed.  Air  enters  the  nostrils,  passes  along  the 
nasal  passages  above  the  hard  palate,  back  of  the  soft 
palate  and  epiglottis,  through  the  open  glottis  into  the 
windpipe,  and  on  to  the  lungs. 

The  Process  of  Swallowing.  — When  the  morsel  of  food 
is  ready  to  be  swallowed  the  tongue  pushes  it  back  into 
the  pharynx;  the  soft  palate  is  raised  to  shut  off  the 
passage  into  the  nasal  cavity ;  the  epiglottis  is  pulled  down 


ustachian  Tube 
Soft  Palate,  Raised 
Food 

Epiglottis,  Down 
Gullet,  Open 

Glottis,  Closed 


Fig  71.  Positions  of  the  Organs  of  the  Mouth  and  Throat  during  Swallowing. 

over  the  glottis,  or  opening  of  the  windpipe;  and  the  base 
of  the  tongue  extends  back  over  the  epiglottis;  thus  the 
air  passages,  above  and  below,  are  shut  off,  and  the  food 
passes  over  the  epiglottis  into  the  gullet.  The  muscles  of 
the  pharynx  also  do  their  part  in  pushing  the  food  along. 
As  soon  as  the  food  has  passed  over  the » epiglottis,  the 
epiglottis  rises  to  its  upright  position,  and  the  soft  palate 
drops  back  to  its  place,  leaving  the  air  passages  again 
open. 


158  Physiology. 

Breathing  and  Swallowing.  —  It  is  to  be  observed  that 
the  food  tube  and  the  air  tube  cross,  and  that  the  pharynx 
is  their  crossing.  As  we  are  swallowing  only  a  small  part 
of  the  time,  the  passageway  naturally  stands  open  to  the 
air;  and  when  we  swallow,  the  parts  are,  by  muscular 
effort,  temporarily  arranged  for  this  work.  There  is  a 
spring  switch  (to  borrow  a  term  from  the  railway)  which 
keeps  the  track  open  for  the  air,  which  is  all  the  time 
passing ;  but  when  the  food  comes  along,  the  switch  must 
close  the  air  passage  and  hold  open  the  food  passage  until 
the  food  has  passed. 

Structure  and  Action  of  the  Gullet  —  The  gullet  has 
an  outer  muscular  coat  and  an  inner  mucous  coat  (see 
Fig.  72).  The  muscular  coat  has  two  layers,  an  inner 
with  circularly  arranged  fibers,  and  an  outer  layer  with 
fibers  running  lengthwise.  When  the  food  enters  the  gul- 
let the  muscle  fibers,  especially  the  circular  fibers,  shorten, 
and  by  a  wave-like  action  push  the  mass  rapidly  along  into 
the  stomach.  The  first  part  of  swallowing  is  voluntary ; 
but  after  the  mouthful  has  entered  the  gullet  the  action  is 
involuntary.  The  mucous  lining  of  the  gullet  has  many 
mucous  glands  which  make  the  passageway  smooth  by  the 
mucus  which  they  secrete. 

Illustration  of  Passage  through  the  Gullet.  —  The  passage  of  the  food 
through  the  gullet  may  be  illustrated  as  follows :  Let  several  persons 
hold  a  large  rubber  tube  with  their  hands  in  contact.  Put  an  egg-shaped 
piece  of  wet  soap  in  the  tube.  The  first  hand  is  shut  and  pushes  the 
soap  along  into  the  part  of  the  tube  held  by  the  next  hand  ;  this  hand 
now  compresses  the  tube,  while  the  first  hand  remains  clinched ;  and  so, 
in  turn,  the  object  is  pushed  the  whole  length  of  the  tube. 

The  Stomach.  —  Just  below  the  diaphragm  the  digestive 
tube  widens  suddenly,  forming  the  stomach ;  the  stomach 


Digestion  in  the  Stomach.  159 

is  an  oval  sac  lying  just  beneath  the  diaphragm,  with  the 
large  end  to  the  left  and  the  small  end  to  the  right.  The 
smaller  end,  by  narrowing,  becomes  the  small  intestine. 
When  the  stomach  is  empty  it  collapses,  as  its  walls  are 
soft  and  flexible.  When  distended  it  may  hold  three  pints, 
or,  when  greatly  distended,  even  more. 

The  Coats  of  the  Stomach.  —  The  stomach  and  intestines  have  four 
coats,  in  the  following  order,  beginning  at  the  outside  :  the  peritoneum, 
the  muscular,  the  submucous,  and  the  mucous  coats.  The  muscular 
coat  of  the  stomach  consists  of  three  layers,  distinguished  by  the  arrange- 


ILLET 


SMALL 
NTESTINE 


Fig.  72.     Longitudinal  Section  of  Stomach,  showing  Gastric  Glands  in  Position. 
(Back  View.    Mucous  Coat  unduly  Thickened.) 

ment  of  the  fibers,  a  circular  layer,  a  longitudinal  layer,  and  an  oblique 
layer.  The  mucous  lining  is  somewhat  loosely  attached  to  the  muscular 
coat  by  the  submucous  coat  between  them,  and  when  the  stomach  col- 
lapses, the  mucous  coat  is  thrown  into  folds,  usually  running  lengthwise. 

The  Gastric  Glands.  —  In  the  inner  surface  of  the  mucous 
membrane  are  many  holes.  These  are  the  mouths  of  the 
ducts  of  the  gastric  glands.  If  a  duct  is  traced  inward,  it 
is  found  to  be  either  a  simple  tube  (see  Fig.  73)  or  to  divide 
into  branches,  usually  two  or  three. 


i6o 


Physiology. 


The  Gastric  Juice.  —  The  liquid  secreted  by  these  glands 
is  called  the  gastric  juice.  The  gastric  juice  is  chiefly 
water,  containing  a  substance  called  pepsin,  and  a  small 
amount  of  acid.  The  amount  of  gastric  juice  secreted 
daily  has  been  estimated  at  four  or  five  quarts.  Of  course, 
we  must  bear  in  mind  that  nearly  all  of  this  is  again 
absorbed  from  the  digestive  tube,  and  is  not  a  loss  to  the 
body. 

Blood  Supply  of  the  Stomach.  —  The  mucous  membrane 
is  well  supplied  with  blood-tubes,  but  while  it  is  resting  the 

blood    flow    is    dimin- 

Mouth  of  Giand          Epithelium  ished,   and  it  is    pale. 

But  as  soon  as  food 
is  introduced  into  the 
stomach  the  blood  flow 
is  greatly  increased, 
and  the  mucous  mem- 
brane becomes  red. 
This  blood  supply  gives 
the  glands  the  materi- 
als with  which  they 
manufacture  the  gastric 
juice.  At  the  same 
time  the  cells  of  the 

glands  are  stimulated  to  action,  and  the  secretion  is  poured 
out  rapidly.  The  saliva  also  aids  in  stimulating  the  secre- 
tion of  the  gastric  j-uice. 

The  Work  of  the  Gastric  Juice.  —  The  special  work  of  the 
gastric  juice  is  accomplished  by  the  pepsin,  aided  by  the 
acid ;  these  change  proteids  into  a  soluble  substance,  called 
peptone,  which  can  be  absorbed  through  the  walls  of  the 
digestive  tube  into  the  blood. 


Connective  Tissue 
Fig.  73.    Three  Glands  of  the  Stomach. 


Digestion  in  the  Stomach.  161 

Rennet  and  Rennin.  —  Rennet,  used  in  cheese  making,  is  a  familial 
substance  obtained  from  the  fourth  stomach  of  the  calf.  When  milk 
enters  the  stomach  it  is  curdled  ;  that  is,  the  casein  previously  dissolved 
in  the  liquid  milk  is  curdled.  This  curdling,  or  coagulation,  is  caused 
by  a  substance  in  the  gastric  juice  called  rennin. 

The  Action  of  the  Stomach.  —  At  the  same  time  all  the 
food  is  soaked  by  the  gastric  juice,  the  process  being 
greatly  assisted  by  the  churning  motion  of  the  stomach 
caused  by  the  action  of  the  muscular  coat.  This  muscular 
action  of  the  stomach  is  called  the  peristaltic  action.  The 
food  is  thus  gradually  reduced  to  a  pulpy  mass  called 
chyme.  During  the  first  part  of  digestion  in  the  stomach 
the  thick  ring  of  circular  fibers,  called  the  pylorus  (gate- 
keeper), around  the  opening  from  the  stomach  into  the 
intestine,  keeps  the  passage  nearly  closed,  leaving  a  small 
hole  for  liquids  only.  But  as  the  food  is  reduced  to  the 
proper  condition  the  muscles  relax  and  allow  the  chyme  to 
pass  into  the  intestine.  And  at  last  any  indigestible  sub- 
stances are  usually  allowed  to  pass. 

Sphincter  Muscles.  —  Such  rings  of  muscular  fibers  as 
the  pylorus,  guarding  openings,  are  called  sphincter 
muscles. 

Time  of  Stomach  Digestion.  —  The  time  required  for  the 
stomach  digestion  of  a  meal  is  from  three  to  four  hours, 
though  this  may  be  much  longer  if  very  indigestible  sub- 
stances have  been  eaten,  or  if  the  condition  of  the  body 
or  mind  is  such  as  to  retard  the  process  of  digestion. 

Chyme.  —  The  rest  of  the  food,  now  called  chyme,  is 
passed  on  into  the  small  intestine.  It  is  acid,  and  in  a 
liquid  or  semiliquid  condition.  Chyme,  as  it  enters  the 
intestine,  is  a  mixture  of  digested,  partly  digested,  and 
undigested  materials.  Some  of  the  starch  has  been  changed 


1 6  2  Physiology. 

to  sugar,  but  only  a  small  part,  owing  to  the  short  time  of 
mastication.  The  bulk  of  the  starch  is  unchanged.  Some 
of  the  proteid  is  already  changed  to  peptone.  Part  is  still 
proteid,  while  part  is  in  an  intermediate  stage  between 
proteid  and  peptone.  Fat  is  melted  by  the  heat  of  the 
mouth  and  stomach,  and  is  more  or  less  divided  into  small 
drops  by  mastication  and  the  movements  of  the  stomach. 
For  instance,  in  eating  bread  and  butter,  the  melting  butter 
will  be  finely  mixed  with  the  bread  as  it  is  chewed.  The 
water  in  the  chyme  was  partly  taken  as  such,  and  partly 
derived  from  the  saliva  and  gastric  juice.  There  are  also 
present  ptyalin,  pepsin,  mucus,  salts,  and  some  indigestible 
substances.  At  intervals  the  sphincter  muscles  of  the 
pylorus  relax,  and  the  contractions  of  the  stomach  send  the 
liquid  mixture  into  the  intestines  by  spurts. 

Heart-burn.  —  Heart-burn  is  a  burning  feeling  in  the 
stomach  and  lower  part  of  the  chest  caused  by  indigestion. 
There  is  a  fermentation  in  the  stomach,  usually  producing 
an  acid  or  sour  stomach. 

Summary.  —  i .  The  pharynx  opens  into  the  mouth,  nostrils,  wind- 
pipe, and  gullet. 

2.  In  breathing,  air  passes  through  the  nostrils  and  the  pharynx, 
and  enters  ,the  windpipe ;   the  soft  palate  is  down  and  the  epiglottis 
is  up. 

3.  In  swallowing,  food  passes  from  the  mouth,  through  the  pharynx, 
into  the  gullet;  the  soft  palate  is  raised  and  the  epiglottis  is  pressed 
down,  covering  the  opening  into  the  windpipe. 

4.  Food  is  pushed  along  the  gullet  by  the  shortening  of  the  ring- 
like  muscles. 

5.  The  stomach  is  pear-shaped,  with  the  large  end  to  the  left. 

6.  The  stomach  has  four  coats,  —  serous,  muscular,  submucous,  and 
mucous. 

7.  The  gastric  glands  are  tube-like  pits  in  the  mucous  coat  of  the 
stomach.     They  make  gastric  juice. 


Digestion  in  the  Stomach.  163 

8.  The  mucous  coat  of  the  stomach  contains  more  blood  during 
digestion,  and  is  more  red,  than  when  resting. 

9.  Pepsin  in  the  gastric  juice  changes  proteids  to  peptones. 

10.  The  muscles  of  the  stomach  wall  give  a  churning  motion. 

1 1 .  The  food  is  reduced  to  a  thick  liquid  called  chyme. 

12.  The  stomach  requires  three  or  four  hours  to  digest  a  meal. 

Questions.  —  i.  Why  is  one  more  likely  to  choke  if  he  thinks  about 
the  process  of  swallowing? 

2.  What  are  the  peculiarities  of  a  cow's  stomach? 

3.  What  is  the  "  rice  ordeal "  ?     What  can  we  learn  from  it? 

4.  Why  do  athletes  eat  sparingly  before  a  game? 

.     5.    How  does  indigestion  sometimes  make  one  short-winded? 

6.  Why  is  it  uncomfortable  to  hold  the  organs  in  the  "  swallowing 
position"? 

7.  Why  is  it  hard  to  swallow  a  pill ?    Why  take  water  with  it? 

8.  Try  swallowing  repeatedly.     Why  is  it  difficult? 

9.  How  is  the  structure  of  the  windpipe  favorable  to  swallowing? 
10.   Why  is  indigestion  more  noticeable  in  the  stomach  than  later? 


CHAPTER   XVII. 
DIGESTION  IN  THE  INTESTINE. 

The  Parts  of  the  Intestine. — The  intestine  consists  of  two 
parts :  first,  the  long  and  narrow  small  intestine ;  second, 
the  short  and  wide  large  intestine.  (See  Fig.  76.) 

The  Small  Intestine. — The  small  intestine  has  essentially 
the  same  structure  as  the  parts  of  the  digestive  tube  already 
studied;  namely,  a  muscular  coat  and  a  mucous  lining.  The 
muscular  coat  has  two  layers,  one  of  circular  and  the  other 
of  longitudinal  fibers.  The  muscular  coat  mixes  the  juices 
with  the  food  and  moves  it  along.  The  muscular  action 
of  the  intestines  is  a  slow  writhing  motion,  called  peristaltic 
action.  The  mucous  coat  supplies  mucus,  which  keeps 
the  surface  soft  and  smooth. 

The  Liver. — The  liver  is  just  under  the  diaphragm.  It 
is  convex  above,  where  it  fits  the  hollow  under  surface  of 
the  diaphragm,  and  hollow  below,  where  it  fits  over  the 
upper  surface  of  the  stomach.  The  greater  part  of  it  is 
on  the  right,  as  the  greater  part  of  the  stomach  is  on  the 
left,  side  of  the  body.  The  liver  is  dark  colored  and  of 
very  delicate  structure,  chiefly  because  it  has  very  little 
connective  tissue.  It  is  the  largest  gland  in  the  body, 
weighing  nearly  four  pounds. 

Bile.  —  Bile  is  a  bitter,  golden  red,  or  sometimes  greenish 
yellow,  liquid  made  by  the  liver  from  the  blood.  About 
two  and  a  half  pints  of  bile  are  made  daily. 

164 


Digestion  in  the  Intestine.  165 


The  Bile  Sac. — This  is  a  sac  of  about  the  size  and  shape 
of  a  pear,  and  is  attached  to  the  under  surface  of  the  liver. 
It  has  a  duct,  the  bile  duct,  which  empties  into  the  small 
intestine  a  few  inches  beyond  the  stomach.  Part  of  the 


Sublingual 
I i vary  Gland 


Pancreas  and 
Duct 

Receptacle  of 

Chyle 
Lacteals 

Mesentery 


Intestine 
Fig-  74.    The  Organs  which  change  Food  into  Blood. 

bile  is  at  once  poured  out  into  the  intestine,  but  part, 
especially  when  we  are  not  digesting,  is  stored  in  the  bile 
sac,  to  be  poured  out  during  digestion. 

Functions  of  Bile.  —  T.    It  aids  in  emulsifying  the  fats. 
2.    It  aids  in  the  absorption  of  fat 


1 66  Physiology. 

3.  The  bile,  to  a  certain  extent,  is  waste  matter;  so  the 
liver  is  an  organ  of  excretion  as  well  as  an  organ  of  secretion. 

4.  It  is  found  that  if,  for  any  cause,  the  bile  is  prevented 
from  entering  the  intestine,  constipation  follows,  and  the 
contents  of  the  large  intestine   have  a  much  more  fetid 
odor  than  usual.     The  bile  retards  this  putrefaction. 

The  Pancreas.  — Just  back  of  the  stomach  is  another  im- 
portant gland,  the  pancreas.  It  is  a  pink  organ,  weighing 
three  or  four  ounces  and  having  the  shape  of  a  dog's 
tongue.  It  has  a  duct  which  empties  into  the  small  intes- 
tine at  the  same  point  where  the  bile  enters,  but  it  has  no 
sac  in  which  to  store  the  liquid  which  it  secretes.  It  takes 
from  the  blood  certain  materials  and  makes  a  liquid  called 
pancreatic  juice. 

Pancreatic  Juice.  —  This  is  a  clear,  sticky  liquid,  very 
much  like  saliva  in  appearance.  Although  the  pancreas  is 
a  small  organ,  its  work  is  very  important.  It  gets  a  large 
blood  supply  and  makes  a  large  amount  of  pancreatic  juice. 
The  pancreas  of  calves  is  often  eaten,  being  known  by  the 
name  "sweetbread." 

The  Work  of  the  Pancreatic  Juice.  —  The  pancreatic  juice 
acts  on  all  the  principal  classes  of  foodstuffs :  — 

1.  A  substance  in  it  called  amylopsin  acts  on  starches, 
changing  them  to  sugar  even  more  actively  than  the  ptyalin 
of  the  saliva. 

2.  Another  substance  in  pancreatic  juice  is  trypsin  ;  like 
the  pepsin  of  gastric  juice,  it  changes  proteids  to  peptones. 

3.  The  pancreatic  juice  also  emulsifies  the  fats.     The 
fat  is  divided  into  exceedingly  fine  drops,  each  covered 
with  a  coating  of  albumen.     An  emulsion  can  be  made 
artificially  by  shaking  together  water,  oil,  and  white-of-egg, 


Digestion  in  the  Intestine*  167 

The  shaking  breaks  the  oil  into  fine  drops,  which  would 
soon  gather  again  if  no  other  substance  were  present ;  but 
the  albumen  forms  a  thin  coating  around  each  droplet, 
enabling  it  to  remain  distinct  in  the  liquid. 

The  Intestinal  Glands. — The  mucous  membrane  of  the 
small  intestine  has  an  immense  number  of  tube-like  glands. 
(See  Fig.  78.)  Their  structure  is 
much  like  that  of  the  gastric  glands 
shown  in  Fig.  73.  Fig.  75  shows 
them  as  seen  when  cut  across. 
These  glands  make  a  liquid  called 
intestinal  juice,  which  completes  the 
work  of  the  other  digestive  liquids. 

Review  of   Digestive  Liquids. - 

Saliva  acts  only  on  starch,  gastric 
juice  on  proteids,  bile  on  fats;  but 

pancreatic  juice  acts  on  all  three.        the  intestine,  showing  intestinal 

Glands    in    Transverse    Section. 
mi.      T  T    ±     ^  T-i.  •  (Highly  magnified.) 

The  Large  Intestine.  —  This  con- 
sists mainly  of  the  colon,  the  final  portion  being  called  the 
rectum. 

The  Colon.  —  The  small  intestine  joins  the  colon  near  the 
lower  right  side  of  the  abdomen.  Where  the  small  intes- 
tine enters  the  colon  there  is  a  valve  which  keeps  the 
material  from  coming  back  into  the  small  intestine.  The 
colon  runs  upward  on  the  right  side  (ascending  colon), 
crosses  over  to  the  left  side  (transverse  colon),  and  descends 
on  the  left  side  (descending  colon),  and,  after  curving  some- 
what like  a  letter  S,  becomes  straight  again,  this  part  being 
called  the  rectum.  It  is  well  to  know  the  course  of  the 
lower  bowel,  as  pressure  may  be  so  applied  as  to  push  the 
contents  along  in  case  the  bowels  become  torpid.  (Fig.  76.) 


i68 


Physiology. 


Gullet 


Stomach 
Duodenum 


Review  of  the  Digestive  Tube.  —  The  whole  digestive 
tube  may  be  briefly  and  roughly  described  as  a  muscular 

tube  of  varying  diameter, 
lined  by  mucous  mem- 
brane. The  muscular  coat 
pushes  the  contents  along 
and  mixes  them  with  liq- 
uids; the  mucous  coat  is 
beset  with  glands,  making 
liquids,  some  of  which 
merely  soak  the  food, 
others  act  on  it  chemically, 
|  while  mucus  serves  to 
|  make  the  surface  slippery, 
o  It  seems  that  these  myriads 
§  of  simple  glands  are  not 
enough,  so  several  large 
compound  glands  lie  along- 
side the  food  tube  and 
empty  their  secretions  into 
it  by  ducts;  these  com- 
pound glands  are  the  sali- 
vary glands,  the  pancreas, 

Fig.  76.    The  Stomach  and  Intestines.          an<3  the  liver. 

Length  of  the  Intestine.  — The  length  of  the  small  in- 
testine is  about  twenty-five  feet,  and  of  the  large  intestine 
five  or  six  feet.  The  large  intestine  is  not  a  direct  contin- 
uation of  the  small ;  that  is,  the  small  intestine  opens  at  a 
right  angle  into  the  large  near  the  beginning  of  the  latter, 
so  that  there  is  a  short  blind  end  called  the  cecum  (see 
Fig.  76).  In  some  animals  this  is  large  and  has  consider- 
able length,  but  in  man  it  is  very  short.  There  is  a  closed 


Vermiform 
Appendix 


Rectum 


Digestion  in  the  Intestine.  169 

prolongation  of  the  cecum,  the  vermiform  appendix.  This 
appendix  is  frequently  the  seat  of  serious  or  fatal  inflam- 
mation, called  appendicitis.  This  disease  is  not  usually 
caused  by  the  lodging  of  seeds  in  the  cecum,  as  most 
people  suppose ;  still  it  is  better  not  to  swallow  such  things. 

A  Simple  Gland.  —  A  gland  is  a  structure  which  takes 
liquid  from  the  blood  and  pours  it  out  on  some  surface. 
In  its  simplest  form  a  gland  is  a  mere  pit,  or  hole,  such  as 
the  gastric  glands,  shown  in  Fig.  73.  The  blood  capilla- 
ries give  off  lymph  around  the  gland,  and  from  this  lymph 
the  cells  of  the  gland  take  their  material.  A  sweat  gland 
needs  more  length  than  a  gastric  gland,  and  the  extra 
length  is  coiled  up  in  a  ball  at  the  inner  end.  Many 
small  glands  are  forked  at  their  inner  ends,  thus  increas- 
ing their  surface. 

Kinds  of  Glands.  —  Fig.  77  shows  different  forms  of 
glands,  from  the  simplest  to  the  most  complex.  In  the 
compound  glands  the  lining  of  the  duct,  which  is  merely 
a  passageway,  is  different  from  the  rest  of  the  gland. 
Glands  that  take  waste  matter  from  the  blood  are  called 
excretory  glands,  such  as  sweat  glands ;  they  do  not  usu- 
ally make  much  change  in  the  material.  Such  glands  as 
the  gastric  glands  change  the  material  that  they  pour  out; 
the  gastric  juice  is  different  from  anything  found  in  the 
blood.  Such  glands  are  called  secretory  glands.  Sweat  is 
an  excretion  ;  gastric  juice  is  a  secretion.  Still,  all  glands 
are  said  to  secrete,  that  is,  to  separate  something  from  the 
blood.  And  gland  action  in  general  is  called  secretion. 
In  structure,  then,  glands  may  be  simple  or  compound. 
In  function  they  may  be  excretory  or  secretory. 

Control  of  Glands.  —  All  glands  are  under  the  control 
of  nerves.  But  this  control  is  involuntary,  and  under  the 

12 — PHY 


1 70  Physiology. 

management  of  the  sympathetic  nervous  system.  The 
mouth  may  "water"  for  some  attractive  food,  or  become 
dry  through  fear  or  anxiety.  Hence  we  can  see  why  a 
restful,  contented  condition  of  mind  and  body  will  be 
likely  to  favor  the  action  of  the  many  glands  along  the 
digestive  tube ;  and,  on  the  other  hand,  why  anxiety  or 
fretfulness  are  likely  to  hinder  their  action. 

Epithelium  or  Epidermis. 
I 


Compound  Glands 
Fig.  77.    Simple  and  Compound  Glands. 

Summary.  —  I .  The  intestine  has  two  coats,  an  outer,  muscular,  and 
an  inner,  mucous,  coat. 

2.  The  intestine  consists  of  two  parts,  the  small  intestine  and  the 
large. 

3.  The  liver  is  the  largest  gland  in  the  body.     It  secretes  bile,  which 
is  stored  in  the  bile  sac. 

4.  Bile  aids  in  emulsifying  and  absorbing  fats,  and  retards  putre- 
faction.    Bile  is  partly  waste  matter. 

5.  The    pancreas    is    a   small   tongue-shaped  organ  back  of  the 
stomach.     It  secretes   the  pancreatic  juice. 


Digestion  in  the  Intestine.  171 

6.  Pancreatic  juice  acts  on  proteids,  fats,  and  starch. 

7.  In  the  walls  of  the  intestine  are  many  small  intestinal  glands. 
Their  secretion  helps  complete  the  process  of  digestion. 

8.  The  main  part  of  the  large  intestine  is  the  colon.     It  has  three 
parts,  ascending,  transverse,  and  descending.     The  last  part  of  the 
intestine  is  the  rectum. 

9.  The  small  intestine  is  twenty-five  feet  long,  the  large,  five  or  six. 

10.  A  gland  is  a  hollow  structure  that  secretes  a  liquid  from  the 
blood. 

1 1 .  Glands  are  simple,  like  an  intestinal  gland,  or  complex,  like  the 
pancreas. 

12.  Glands  are  excretory,  such  as  the  sweat  glands,  or  secretory, 
such  as  the  gastric  glands. 

Questions.' — i.  Why  is  there  such  a  difference  in  the  lengths  of 
intestine  in  the  cat  and  the  cow? 

2.  What  is  biliousness? 

3.  Why  is  the  pancreas  sometimes  called  the  "abdominal  salivary 
gland1'? 

4.  Why  does  digestion  proceed  more  slowly  in  the  intestine  than 
in  the  stomach? 

5.  In  what  direction  should  the  abdomen  be  rubbed  to  assist  a 
movement  of  the  bowels? 


CHAPTER  XVIII. 
ABSORPTION. 

Absorption  a  Living  Process.  —  The  layer  of  cells  which 
forms  the  inner  surface  of  the  mucous  membrane  is  called 
epithelium.  These  cells  are  moist,  soft,  and  thin-walled. 
They  take  up  the  digested  foods,  now  in  liquid  form,  and 
pass  them  on  to  the  lymph  and  so  into  the  blood  capillaries 
that  are  thickly  distributed  just  beneath  the  surface. 

Absorption  from  the  Mouth.  —  Sugar,  and  some  other 
substances,  may  be  absorbed  by  the  mouth  as  soon  as  it  is 
dissolved.  But  very  little  material  is  thus  absorbed. 

Absorption  from  the  Stomach.  —  Some  parts  of  the  food 
that  are  already  digested,  or  such  matters  as  are  soluble, 
e.g.  water  containing  sugar,  peptone,  salts,  etc.,  may  be 
absorbed  immediately  through  the  walls  of  the  stomach 
into  the  blood  capillaries.  Recent  experiments  show,  how- 
ever, that  the  amount  of  absorption  from  the  stomach  is 
much  less  than  was  formerly  supposed;  water,  for  instance, 
"  when  taken  alone,  is  practically  not  absorbed  at  all  in  the 
stomach.  As  soon  as  water  is  introduced  into  the  stomach 
it  begins  to  pass  out  into  the  intestine,  being  forced  out  in 
a  series  of  spurts  by  the  contractions  of  the  stomach." 

Absorption  from  the  Small  Intestine.  —  Most  of  the 
digested  food  is  absorbed  in  the  small  intestine. 

Increased  Surface  for  Absorption. — The  mucous  mem- 
brane of  the  small  intestine  is  thrown  into  ridges,  but, 
unlike  those  of  the  stomach,  they  run  crosswise.  Again, 

172 


Absorption. 


173 


Villuses 


while  the  folds  in  the  lining  of  the  stomach  are  temporary, 
these  are  permanent.  They  increase  the  surface  of  the 
lining  and  retard  the  passage  of  the  food  material,  and  so 
aid  the  process  of  digestion  and  of  absorption. 

Villuses.  —  To  increase,  still   further,  the   surface   for 
absorption,  the  mucous  membrane  of  the  small  intestine  is 

thickly  covered  with 
little  cylindrical  pro- 
jections, like  the 
"pile"  on  velvet. 
Each  of  these  pro- 
jections is  a  villus. 

Intestinal  Glands  ^B 

Structure  of  a  Vil- 
lus. —  A  villus  is 
about  a  thirtieth  of 
an  inch  long.  It  is  made  up  of  four  parts  :  ( I )  on  the  out- 
side a  layer  of  soft,  moist,  thin-walled  cells;  (2)  plain 
muscle  fibers,  running  lengthwise ;  (3)  a  network  of  blood 


Fig.  78.     Mucous  Membrane  of  Small  Intestine,  showing 
Intestinal  Glands  and  Villuses,  greatly  Magnified. 


Lacteal  with  Valves  Capillaries  Muscles  Epithelium 

Fig.  79.     Four  Parts  of  a  Vilius,  greatly  Magnified. 

capillaries ;  and  (4),  near  the  center,  lymph  capillaries, 
called  lacteals.  Fig.  79  shows  these  four  parts  separate, 
while  Fig.  80  shows  them  combined,  as  they  are  in  the 
complete  villus. 


1 74  Physiology. 

Absorption  by  the  Villuses.  —  The  digested  food  is  in 
liquid  form  and  surrounds  the  villuses.  The  three  main 
substances  to  be  absorbed  are  peptones,  sugar,  and  fat. 
The  outer  cells  of  each  villus  absorb  these  and  pass  them 
inward.  The  peptones  and  sugars  are  taken  into  the  blood 
capillaries,  while  the  fats  enter  the  lacteals. 

Muscular  Action  of  the  Villuses.  —  In  each  villus  there 
are  plain  muscle  fibers.  When  these  shorten  they  squeeze 
the  chyle,  that  has  already  been  absorbed,  into  the  lymph 
tubes  of  the  wall  of  the  intestines,  and  on  into  the  main 


Epithelial  Covering 


Lacteal 

Longitudinal  Mus- 
cular Fibers 
Capillary  Network 


Fig.  80.    A  Complete  Villus,  very  greatly  Magnified. 

lymph  duct.  The  chyle  cannot  return  to  the  lacteal  when 
the  muscles  relax,  on  account  of  the  valves,  similar  to 
those  of  the  veins,  in  the  lacteal  at  the  base  of  the  villus. 
Then,  when  the  muscles  relax,  the  lacteal  is  empty,  and 
ready  to  absorb  more  of  the  emulsified  fat  that  we  call 
chyle.  This  action  also  helps  the  flow  in  the  blood 
capillaries. 

The  Lacteals  and  Lymphatics.  —  While  the  main  work 
of  the  lymphatics,  as  we  have  seen,  is  the  carrying  of 
lymph  from  the  tissues  of  the  body  to  empty  into  the 
veins  of  the  neck,  the  lymphatics  of  the  intestines  have 
another  important  function.  They  absorb  and  carry  the 
fatty  portions  of  the  digested  food  into  the  general  circu- 
lation. During  most  of  the  time  the  thoracic  duct  and 


Absorption. 


175 


the  lymphatics  of  the  intestines  would  hardly  be  noticed 
because  they  are  filled  with  the  clear  lymph.     But  after 


Right  Lymph  Vein 


Junction  of  Thoracic 
Duct  with  LeftSub- 
clavian  Vein 


Main  Lymph  Vein 
(Thoracic  Duct) 


Intestine 


Lymphatic  Glands 


Fig.  81.     Lymph  Veins  (Lymphatics). 

absorption  of  fatty  matter  they  are  filled  with  a  white 
liquid,  called  chyle,  and  are  easily  seen.     (See  Fig.  81.) 

The  Portal  Circulation. — All  the  veins  coming  from  the 
stomach  and  intestines  unite  to  form  a  large  vein  that  goes 
to  the  liver ;  this  is  the  portal  vein.  When  the  portal  vein 
enters  the  liver  it  does  what  veins  do  not  do  elsewhere  in 
the  body, — it  divides  into  smaller  branches.  This  division 


i76 


Physiology. 


and  subdivision  goes  on  till  the  portal  vein  forms  capil- 
laries branching  all  through  the  liver. 

The  blood  from  these  capillaries  collects  again  in  veins, 
which  unite  in  one  vein,  the  hepatic  vein,  which  carries 
the  blood  into  the  postcaval  vein  just  under  the  diaphragm. 


Fig.  82.    Diagram  of  Portal  Circulation. 

Going  back  again  to  the  beginnings  of  the  portal  vein, 
it  is  clear  that  it  starts  from  the  capillaries  of  the  stomach 
and  intestines.  And  these  capillaries,  as  we  have  just  seen, 
absorb  the  peptones  and  sugars.  The  sugars  and  peptones, 
therefore,  go  directly  to  the  liver  after  being  absorbed. 

Double  Blood  Supply  to  the  Liver. — The  liver  also  re- 
ceives blood  from  the  hepatic  artery,  a  branch  of  the  aorta. 


Absorption. 


177 


Thus  the  liver  gets  blood  from  two  sources,  the  portal  vein 
and  the  hepatic  artery,  but  is  drained  by  one  vein,  the 
hepatic  vein. 

Work  of  the  Liver. — We  have  seen  that  the  liver  makes 
bile.  The  liver  also  makes  another  substance  out  of  the 
blood  that  passes  through  it.  This  is  glycogen,  or  "animal 
starch."  It  is  also  called  "liver  sugar,"  as  it  gives  to  liver 


Portal  Vein 


Mesenteric 

Blood  Veins 

(Albumen, 

Sugar) 


Capillaries 


Fig.  83.    Plan  of  Absorption. 

a  sweetish  taste.  Glycogen  is  given  back  to  the  blood  and 
carried  away  by  the  hepatic  vein  to  the  body,  where  it 
serves  as  food  to  the  tissues. 

Routes  of  Different  Foods  after  Absorption. —There  are, 
then,  two  routes  taken  by  the  food  after  absorption.  The 
peptones  and  sugars  go  to  the  liver  through  the  portal 


i78 


Physiology. 


vein,  while  the  fats  are  carried  by  the  main  lymph  duct,  or 
thoracic  duct.  These  two  streams  unite  before  reaching 
the  heart.  The  fats  pass  around  the  liver,  instead  of 
through  it  as  do  the  peptones  and  sugars. 


PARTS 
OF 
DIGESTIVE 
TUBE. 

MECHANI- 

GLANDS. 

LIQ- 
UIDS. 

CHEMICAL 
CHANGE. 

ABSORPTION. 

CAL  PRO- 
CESSES. 

MATERIAL 

BY 

MOUTH. 

Cutting 
and 
Grinding. 

Salivary. 

Saliva. 

Starch 
to 
Sugar. 

PHARYNX. 

Raising  Soft 
Palate. 
Depressing 
Epiglottis. 

GULLET. 

Food  carried 
to  Stomach. 

Mucous. 

Mucus. 

STOMACH. 

Churning 
and 
Mixing. 

Gastric. 

Gastric 
Juice. 

Proteid 
to 
Peptone. 

Water.      ] 
Salts.          1 
Sugars.      j 
Peptones.  J 

Blood 
Capillaries. 

SMALL 
INTESTINE. 

Mixing 
and 
Moving 
Food. 

Liver. 
Pancreas. 

Intestinal. 

Bile. 
Pancreatic 
Juice. 
Intestinal 
Juice. 

(  Starch  to  Sugar. 
j  Proteid  to  Peptone. 
j  p       t  Emulsified. 
L          '  Decomposed. 

Water.      ] 
Salts.          [ 
Sugar.        1 
Peptone.    ! 
Fats. 

Blood 

Capillaries. 

Lacteals. 

LARGE 
INTESTINE. 

Food 
Forced  on. 

Mucous. 

Mucus. 

Water. 

Fig.  84.    Outline  of  Digestion  and  Absorption. 

Amount  of  Liquid  Absorbed. — It  is  estimated  that  there 
is  poured  into  the  digestive  tube  daily  one  quart  of  saliva, 
four  or  five  quarts  of  gastric  juice,  one  quart  of  bile,  and 
about  a  quart  of  pancreatic  juice.  If  the  food  and  drink 
amounts  to  two  quarts,  there  must  be  more  than  two  gal- 
lons of  liquid  absorbed  from  the  digestive  tube  each  day. 


Absorption.  1 79 

The  Work  of  the  Large  Intestine.  —  Most  of  the  ab- 
sorption is  accomplished  in  the  small  intestine ;  but  as  the 
food  passes  on  into  the  large  intestine  the  work  of  digestion 
and  of  absorption  is  carried  somewhat  farther.  If  the 
residue  be  not  soon  expelled,  there  may  be  absorption  of 
some  of  the  results  of  putrefactive  changes,  and  a  sort 
of  general  poisoning  of  the  whole  body.  Hence  the 
great  importance  of  regularly  and  thoroughly  emptying 
the  lower  bowel.  The  matter  thus  expelled  is  largely 
made  up  of  indigestible  material,  with  some  real  waste 
substances. 

Taking  up  again  our  comparison  of  the  body  and  a 
stove,  we  see  that  the  feces  are  not  true  waste  products, 
but  are  rather  clinkers,  or  material  that  has  not  been 
burned  or  oxidized  in  the  body.  The  real  wastes  of  the 
body  are  the  carbon  dioxid,  urea,  water,  etc.,  that  are  pro- 
duced by  the  oxidation  of  the  tissues,  and  are  mostly  thrown 
off  by  the  lungs,  kidneys,  and  skin. 

Summary.  —  i.  The  cells  lining  the  digestive  tube  take  up  the 
digested  food,  now  in  liquid  form,  and  pass  it  into  the  lymph. 

2.  There   is  some  absorption,  from  the  stomach,  of  sugar  and 
peptone.     Most  of  the  absorption  is  from  the  small  intestine. 

3.  The  hair-like  villuses  greatly  increase  the  absorbing  surface. 

4.  A  villus  has  four  parts,  the  outer  layer  of  cells,  plain  muscle 
fibers  running  lengthwise,  blood  capillaries,  and  lacteals. 

5.  The  outer  cells  of  the  villus  take  up  the  liquefied  food. 

6.  Sugar    and    proteids    enter  the   blood   capillaries;    fats  enter 
the  lacteal  capillaries. 

7.  The  muscles  of  the  villus  pump  the  liquids  along  and  aid 
absorption. 

8.  The  lacteals  are  part  of  the  lymph  system  of  the  body.     They 
absorb  and  carry  fats. 

9.  The  veins  from  the  stomach  and  intestine  join  to  form  the  por- 
tal vein  which  enters  the  liver.     Here  it  breaks  up  into  capillaries. 


180  Physiology. 

10.  The  liver  has  two  supplies  of  blood,  from  the  portal  vein  and 
the  hepatic  artery.     It  is  drained  by  one  vein,  the  hepatic  vein. 

11.  The  liver  makes  bile  and  glycogen. 

12.  Sugars  and  proteids  go  through  the  liver;  fats  pass  around  the 
liver  through  the  main  lymph  vein,  or  thoracic  vein. 

13.  There  are  over  two  gallons  of  liquids  absorbed  daily. 

Questions.  —  i.    Why  is  it  best  to  begin  a  hearty  meal  with  soup  ? 

2.  Why  should  the  liver  receive  so  much  blood  ? 

3.  What  is  the  meaning  of  "  biliousness  "  ? 

4.  What  is  the  advantage  of  a  "  fruit  diet "  ? 

5.  Why  does  active  exercise  tend  to  keep  the  bowels  open? 


CHAPTER  XIX. 
HYGIENE  OF  DIGESTION.  — NUTRITION. 

Digestion  and  Circulation.  —  During  digestion  there  must 
be  a  large  supply  of  blood  in  the  digestive  organs.  It  is 
needed  both  to  supply  the  material  for  the  glands  to  make 
the  digestive  liquids  and  also  to  absorb  and  bring  away  the 
newly  digested  food.  Therefore,  during  digestion  there 
must  be  less  blood  in  other  parts  of  the  body. 

Digestion  and  Muscular  Work.  —  If  one  exercises  actively 
immediately  after  eating,  the  process  of  digestion  will  be 
interfered  with,  because  the  blood  will  be  drawn  away 
from  the  digestive  organs  to  the  muscles.  It  is  well  to 
rest  for  a  short  time  after  eating  a  full  meal. 

Digestion  and  Study.  —  For  the  same  reason  it  is  better 
not  to  begin  hard  study  immediately  after  a  full  meal.  The 
blood  needed  for  the  work  of  digestion  will  be  called  to  the 
brain,  and  digestion  will  suffer. 

Solid  Foods  digest  Slowly.  —  If  a  very  hungry  person 
begins  his  dinner  with  solid  food,  he  is  likely  to  eat  too 
fast.  Hunger  is  a  demand  of  the  system  for  food.  It 
takes  some  time  for  solid  food  to  go  through  all  the  pro- 
cesses of  digestion,  and  be  absorbed  into  the  system  and 
satisfy  hunger. 

Value  of  Soup.  —  But  if  the  meal  begins  with  soup,  which 
is  readily  absorbed,  the  demand  of  the  system  will  begin  to 
be  met,  and  there  will  not  be  the  same  tendency  to  rapid 

181 


1 8  2  Physiology. 

eating.  Further,  a  warm  soup  stimulates  the  blood  flow  in 
the  mucous  membrane,  and  thus  prepares  for  more  thorough 
digestion. 

Desserts.  —  Dessert  and  sweetmeats,  following  a  meal, 
are  often  helpful  by  further  stimulating  the  secretion  of  the 
glands.  Nuts,  which  are  not  very  digestible,  are  beneficial 
if  eaten  sparingly.  The  agreeable  taste  stimulates  the 
salivary  glands,  and  the  saliva  stimulates  the  gastric  glands 
to  increased  activity.  The  danger  in  taking  dessert  is  that 
the  pleasing  taste  tempts  us  to  continue  eating  after  we 
have  had  enough.  Pie  is  usually  hard  to  digest. 

The  Bad  Effects  of  Imperfect  Mastication.  —  If  we  swallow 
food  before  it  is  thoroughly  ground  and  mixed  with  the 
saliva,  the  stomach  and  other  parts  of  the  digestive  organs 
will  require  much  more  time  to  reduce  the  food  to  a  liquid 
form.  Further,  when  eating  hastily,  we  are  very  apt  to 
eat  too  much.  Thus  we  may  give  the  stomach  a  double 
amount  of  material  to  handle,  and  the  material  may  not  be 
half  so  well  prepared  as  it  should  be.  Of  course  the  organs 
suffer  and  break  down  if  this  treatment  is  continued. 

Effect  of  Repose  on  Digestion.  —  Not  only  mastication,  but 
the  whole  process  of  digestion,  goes  on  better  when  the 
body  and  mind  are  at  rest  and  in  a  peaceful  condition,  as 
all  the  glands  are  under  the  control  of  the  nervous  system, 
and  are  greatly  influenced  by  the  condition  of  the  body. 
During  a  meal,  and  for  a  short  time  before  and  after,  all 
thoughts  of  one's  occupation,  and  especially  all  anxiety, 
should  be  dismissed  from  the  mind.  For  those  whose 
digestion  is  not  strong,  it  is  desirable  to  rest  after  each 
meal. 

Conversation  at  Meals.  —  During  a  meal  there  should  be 
conversation  on  topics  of  general  interest.  Talking  at  the 


Hygiene  of  Digestion.  183 

table  also  makes  us  more  deliberate  in  eating.     "  Chatted 
food  is  half  digested." 

Time  of  Eating.  —  The  American  custom  of  three  meals 
a  day  seems  well  adapted  to  the  needs  of  our  people.  The 
best  time  for  the  chief  meal  is  near  the  middle  of  the  day, 
as  is  the  custom  in  the  country ;  for  the  bodily  powers  are 
higher  than  later  in  the  day.  But  for  city  people,  and 
others  who  are  very  busy  in  the  middle  of  the  day,  it  is 
undoubtedly  better  to  take  the  chief  meal  after  the  rush  of 
the  day's  work  is  over,  when  there  is  time  for  a  deliberate 
meal  and  when  the  mind  is  free  from  business  cares.  In 
many  homes  this  is  the  only  time  when  the  whole  family 
can  leisurely  meet  at  the  table. 

Eating  between  Meals.  —  The  stomach  should  have  time 
to  rest  and  prepare  for  the  work  of  digesting  another  meal. 
Many  find  two  meals  a  day  sufficient.  There  are  some 
persons,  however,  for  whom  it  would  be  better  to  have 
more  meals,  with  less  food  at  a  time.  Meals  should  be 
regular. 

Amount  of  Food  Needed.  —  This  varies  greatly  with  the 
individual,  age,  the  kind  and  amount  of  labor,  etc.,  so  that 
no  very  helpful  rule  can  be  given.  Each  person  must  find 
by  experience  what  is  best  for  himself.  It  is  the  opinion 
of  many  leading  physicians  that  the  majority  of  mankind 
eat  too  much. 

Intemperance  in  Eating.  —  "I  have  come  to  the  conclu- 
sion that  more  than  half  of  the  disease  which  embittei  s  the 
middle  and  latter  part  of  life  is  due  to  avoidable  errors  of 
diet ;  and  that  more  mischief,  in  the  form  of  actual  disease, 
of  impaired  vigor,  and  of  shortened  life,  accrues  to  civilized 
man  from  erroneous  habits  of  eating  than  from  the  habitual 


184  Physiology. 

use  of  alcoholic  drink,  considerable  as  I  know  that  evil  to 
be."  -  -  Thompson. 

Self-denial  in  Eating.  —  It  is  a  good  old  saying,  "  We 
never  repent  having  eaten  too  little."  Nearly  every  one 
has  regretted  having  eaten  too  much.  It  is  better  to 
stop  before  one  has  eaten  quite  as  much  as  he  would 
like,  especially  when  taking  highly-seasoned  or  sweetened 
food. 

Fat  as  a  Tissue.  —  As  a  tissue  fat  serves  as  a  stored-up 
food.  A  fat  person  can  endure  starvation  longer,  other 
things  being  equal,  than  a  thin  person.  A  layer  of  fat 
under  the  skin  serves  also  as  a  heat  saver. 

Hibernation.  —  Hibernating  animals  are  fat  when  they  enter  upon 
their  winter  sleep,  but  are  lean  when  they  come  out  in  the  spring. 
Remaining  inactive,  they  have  produced  very  little  energy,  their  only 
motions  being  a  slow  and  feeble  breathing  and  heart-beat.  They  have 
consumed  the  fat,  using  it  mainly  in  maintaining  the  necessary  heat. 
In  short,  they  have  burned  their  fat  to  keep  them  warm. 

Importance   of    Renewal   of    Blood  and  Lymph.  —  The 

lymph  surrounds  the  individual  cells  which  make  up  the 
tissues  of  the  body.  Every  cell  lives  an  independent  life, 
to  a  certain  extent,  taking  its  nourishment  directly  from 
the  lymph  around  it.  The  importance  of  an  abundant 
supply  of  good  lymph  is  apparent.  The  supply  and  renewal 
of  the  lymph  depends  on  the  blood. 

Effect  of  Digestion  on  Blood  and  Lymph.  —  If  digestion  is 
not  good,  or  if  there  is  not  enough  good  food,  good  blood 
cannot  be  made,  and  the  lymph  will  not  be  good.  The 
cells  are  more  or  less  starved,  or  poisoned  if  wastes  are  not 
properly  removed,  and  the  general  tone  of  the  body  will 
soon  be  lowered;  for  the  health  of  tLe  body  as  a  whole 
depends  on  the  average  condition  of  the  cells  composing 


Hygiene  of  Digestion. 


i85 


the  body,  just  as  the  condition  of  any  community  depends 
on  the  average  condition  of  the  individuals  of  that  com- 
munity. 

Assimilation.  —  The  formation  of  tissue  from  the  mate- 
rials brought  by  the  blood  is  assimilation.  It  is  the  last 
step  in  building  up  the  tissues. 


Capillaries 


Vein 


Arteiy 


Vein 


Capillaries 
Fig.  85.    Diagram  of  the  Heart  and  Blood  Tubes  (Back  ViewV 

Blood  a  Mixture  of  Good  and  Bad.  —  In  the  blood  streams 
are  combined  the  good  and  the  bad.     The  newly  digested 
food  is  received  into  a  current  of  impure  blood  in  the  post- 
13— PHY 


86 


Physiology. 


caval  vein.  The  blood  from  the  kidneys,  probably  the 
purest  blood  in  the  body,  joins  the  same  impure  stream. 
From  the  aorta,  red  blood,  usually  called  pure,  —  the  same 


Lung  Capillaries 

r 


Pulmonary  Vein 


Body  Capillaries 

Fig.  86.    Plan  of  Circulation,  representing  the  Right  and  Left  Halves  of  the  Heart  sepa- 
rated, showing  that  the  Blood  makes  but  One  Circuit. 

kind  that  goes  to  the  brain,  —  is  sent  to  the  kidneys  and  to 
the  skin  to  be  purified.  Yet,  as  this  mixed  blood  flows 
through  each  organ,  that  organ,  so  long  as  it  is  in  health, 
takes  from  it  only  what  it  should  take. 


Hygiene  of  Digestion.  187 

Action  of  Diseased  Kidneys.  —  The  kidney  takes,  during 
health,  only  the  waste  matters,  leaving  the  valuable  nour- 
ishing material.  But,  in  disease,  the  kidneys  may  take  out 
some  of  the  most  valuable  nourishing  material.  Suppose 
that  in  a  mill,  a  workman,  whose  business  is  to  shovel  out 
wastes,  becomes  crazy,  and  shovels  wheat  or  flour  out  of 
the  mill  into  the  stream  below.  The  diseased  kidney  may 
be  said  to  have  become  crazy,  and  in  the  disease  called 
"  diabetes  "  throws  out  sugar,  and  in  "  albuminuria "  ex- 
cretes albumen. 

Blood  Streams  like  Water  Pipes  and  Sewer  Combined.  — 
It  is  as  though  the  water  supply  of  a  city  house  was  taken 
from  the  sewer ;  each  organ  needing  a  supply  of  building 
material  acts  like  a  filter,  taking  from  the  blood  what  it 
needs,  paying  no  attention  to  the  impurities  present,  and 
the  organs  of  excretion  select  the  impurities,  allowing  the 
useful  substances  to  pass  on  to  the  places  where  they  are 
needed.  Figs.  85,  86,  and  87  show  what  the  blood  stream 
gives  to  each  of  the  organs  of  the  body  and  what  it  takes 
from  them  to  throw  out  as  waste  matter. 

How  the  Body  Changes.  —  The  body  is  continually 
changing,  new  material  from  the  digested  food  taking  the 
place  of  the  worn-out  tissues.  It  is  a  common  saying  that 
the  body  changes  once  in-  seven  years.  But  while  the 
more  active  tissues,  such  as  muscle,  must  change  many 
times  in  a  year,  we  know  that  the  teeth  do  not  grow  after 
they  are  once  formed. 

The  Body  like  an  Eddy.  —  The  changes  in  the  body  have 
been  compared  to  an  eddy  in  a  stream.  The  form  of  the 
eddy  remains  the  same,  while  particles  of  water  are  enter- 
ing on  one  side  and  leaving  on  the  other.  In  a  short  time 


1 88  Physiology. 

all  the  particles  are  changed.     But  in  the  body  the  more 
permanent  parts  change  slowly. 

Nutrition.  —  Nutrition  includes  all  the  changes  that  take 
place  in  the  body  from  the  reception  of  food  to  the  excre- 
tion of  the  waste  matter.  It  includes  digestion,  absorption, 
circulation,  assimilation,  respiration  (oxidation),  and  excre- 
tion. The  first  four  of  these  processes  are  stages  in  build- 
ing tip  the  tissues  ;  the  last  two  are  process  of  tearing  doivn. 

We  cannot  destroy  Matter.  —  When  a  stick  of  wood  is 
burned  it  is  no  longer  wood.  But  the  matter  is  not  de- 
stroyed. It  could  all  be  obtained  again  from  the  smoke 
and  ashes.  So,  in  the  continual  wasting  away  of  our 
bodies,  there  is  no  real  loss  of  matter.  Our  weight  is  re- 
duced, but  the  wastes  are  still  part  of  the  earth  or  the  air, 
and  are  of  use  in  the  world.  We  are  as  unable  to  destroy 
matter  as  we  are  to  create  it. 

The  Ceaseless  Round  of  Matter.  —  A  particle  of  carbon 
in  the  carbon  dioxid  of  the  expired  breath  may  be  taken  in 
by  a  blade  of  grass.  A  cow  eats  the  grass,  and  we  may 
before  long  take  the  very  same  particle  of  carbon  in  the 
milk  or  the  flesh  of  the  cow.  Or  the  particle  of  carbon 
may  become  part  of  a  grain  of  wheat,  and  be  made  into 
flour  and  be  eaten  as  bread  and  be  a  part  of  the  body 
once  more.  Thus,  there  is  a-  ceaseless  round  of  matter 
into  and  out  of  our  bodies.  No  one  has  a  monopoly  of 
any  portion  of  matter ;  it  is  now  ours,  now  some  one  else's. 

We  cannot  create  Force. — We  get  our  energy  from  the 
food  we  eat,  just  as  an  engine  gets  its  energy  from  fuel. 
This  is  saying  nothing  against  the  superiority  of  the 
human  body  and  is  not  in  the  least  degrading.  We  are 
living,  growing,  self -directing,  and  self -maintaining  ma* 


Hygiene  of  Digestion.  189 


PULMONARY  VEIN 

LEFT  AURICLE 


LEFT  VENTRICLE 


PULMONARY  ARTERY 

RIGHT  VENTRICLE 

RIGHT  AURICLE 


* 


Fig.  87.    The  Circulation  and  the  Work  of  the  Blood 


i  go  Physiology. 

chines.     Still,  starvation  soon  puts  an  end  to  our  ability 
to  produce  energy  of  any  kind. 

How  we  depend  on  Plants.  —  The  larger  part  of  our  food 
is  vegetable.  And  the  animal  foods,  such  as  meat,  milk, 
cheese,  butter,  eggs,  etc.,  were  made  by  the  animals  from 
vegetable  matter.  We  are,  therefore,  directly  or  indirectly, 
dependent  on  plants  for  all  our  food.  On  the  other  hand, 
plants  use  as  their  food  considerable  of  the  waste  matter 
thrown  off  by  animals. 

Summary.  —  i .  During  digestion  a  large  supply  of  blood  is  required 
in  the  digestive  organs. 

2.  Muscular  work,  immediately  after  eating,  interferes  with  digestion 
by  calling  the  blood  away  to  the  muscles. 

3.  Hard  study,  right  after  a  hearty  meal,  hinders  digestion-  in  the 
same  way. 

4.  Soup  is  a  good  beginning  of  a  hearty  meal,  as  it  is  more  readily 
absorbed  than  solid  food. 

5.  Desserts,  in  moderate  quantity,  are  useful   in   stimulating  the 
glands  which  supply  the  digestive  liquids. 

6.  Hot  drink  at  meals  aids  weak  digestion. 

7.  Imperfect  mastication  leads  to  eating  too  much,  and  throws  too 
much  work  upon  the  other  organs  of  digestion. 

8.  A  calm  condition  of  the  nervous  system  favors  digestion. 

9.  Conversation  on  cheerful  topics  is  favorable  to  digestion. 

10.  Three  meals  a  day  are  best  for  most  persons. 

1 1 .  For  persons  hurried  in  the  middle  of  the  day  it  is  often  better 
to  take  the  chief  meal  at  the  close  of  the  day's  work. 

12.  Meals  should  be  regular,  and  one  should  not  eat  between  meals. 

13.  There  is  much  intemperance  in  eating. 

14.  Fat,  as  tissue,  is  stored  food. 

15.  The  cells  depend  on  the  lymph  for  their  nourishment,  and  the 
lymph  is  supplied  by  the  digested  food. 

1 6.  The  blood  is  a  mixture  of  good  and  bad  material;  each  organ, 
in   health,  selects   from  the  blood  what  it  needs,  the  tissues  taking 
nourishment,    and    the    organs    of    excretion    removing    the    waste 
matters. 


Hygiene  of  Digestion.  191 


17.  Diseased  kidneys   may  remove  valuable   nourishing  materials 
from  the  blood. 

1 8.  The  body  keeps  changing,  taking  new  matter  to  replace  worn- 
out  tissue. 

19.  Nutrition  includes  digestion,  absorption,  circulation,  respiration, 
assimilation,  oxidation,  and  excretion. 

20.  We  cannot  destroy  matter.     Our  waste  products  become  part 
of  earth  or  air. 

21.  We  cannot  create  force.     We  get  our  energy  from  food  as  an 
engine  gets  its  energy  from  fuel. 

22.  We  depend  on  plants  for  our  food. 

Questions.  —  i .  Should  a  person  who  has  studied  hard  try  to  do  hard 
muscular  work  the  same  day  ? 

2.  What  are  the  advantages  of  a  "course"  dinner? 

3.  Which  is  more  wholesome,  dry  toast  or  soaked  toast?    Why? 

4.  Why  do  we  give  a  horse  exercise  and  keep  fattening  stock  quiet? 

5.  Are  fat  people  large  eaters ?     Are  thin  people  light  eaters? 

6.  Do  sweat  glands  ever  excrete  valuable  material  ? 

7.  In  Fig.  87  find  what  the  blood  gives  to  each  organ  and  what  it 
takes  from  each. 

8.  Classify  the  organs  represented  in  Fig.  87. 

9.  Name  the  organs  that  change  most  rapidly. 

10.  Name  the  organs  that  change  most  slowly. 

1 1 .  What  is  the  source  from  which  plants  get  their  energy? 

12.  Is  matter  defiled  in  passing  from  one  body  to  another? 


CHAPTER   XX. 
EXERCISE  AND  BATHING. 

How  Exercise  is  Beneficial.  —  Exercise  stimulates  the 
cells  to  activity  and  renews  the  lymph  around  the  cells 
both  by  quickening  the  blood  flow  and  by  pressure  on  the 
lymph  tubes.  The  glands  of  excretion  are  set  to  work 
more  actively,  and  the  more  rapid  blood  stream  brings 
away  the  material  to  be  thrown  out. 

Exercise  for  General  Health.  —  Exercise  is  not  merely 
for  the  muscles.  It  quickens  the  action  of  the  whole  body 
by  increasing  cell  activity.  It  helps  clean  out  the  system 
and  clear  the  brain  as  well.  It  is  not  so  much  strength  as 
health  that  we  need.  The  ability  to  do  our  daily  work,  to 
do  it  with  comfort  and  without  any  feeling  of  strained 
effort,  is  what  we  need. 

Exercise  prolongs  Life.  —  Many  men  would  live  longer, 
feel  better,  and  do  greater  good  in  the  world,  if  they  took 
regular  and  systematic  exercise.  It  is  a  shortsighted 
policy  to  say,  "I  cannot  afford  the  time."  Not  to  take 
time  for  exercise  is  to  mortgage  one's  future.  "  He  who 
does  not  take  time  for  exercise  will  have  to  take  time  for 
illness."  The  latter  half  of  every  person's  life  ought  in 
many  respects  to  be  by  far  the  most  productive  of  good. 
But  many  cut  off  this  half,  or  render  it  less  useful  through 
breaking  down  in  health  as  a  result  of  violating  the  laws 
of  health. 

192 


Exercise  and  Bathing.  193 

Nature's  Rewards  and  Punishments.  —  Nature  never 
fails  to  punish  every  violation  of  her  laws.  Her  reward 
for  obedience  is  health  and  the  delight  that  accompanies  it. 

Useful  Exercise.  —  The  man,  woman,  boy,  or  girl  who 
has  regular  work  that  calls  for  muscular  activity  is  to  be 
congratulated.  Duty  obliges  them  to  take  regular  exer- 
cise. The  boy  who  has  "  chores "  to  do  is  to  be  envied 
rather  than  pitied. 

Choice  of  Exercise.  —  But  many  persons  are  so  situated 
that  they  have  no  work  to  do.  They  must  choose  some 
exercise  that  is  not  for  a  directly  useful  purpose.  In  se- 
lecting exercise  one  should  choose  (i)  that  which  is  enjoy- 
able, for  exhilarating  exercise  is  much  more  beneficial  than 
that  which  is  taken  as  a  necessity ;  (2)  exercise  should  be 
in  the  open  air  whenever  possible. 

Forms  of  Exercise.  —  There  is  a  great  variety  of  forms 
of  exercise  from  which  each  person  can  select  according 
to  his  age,  strength,  etc.  For  active  youths  there  are  run- 
ning, jumping,  wrestling,  boxing,  fencing,  hare  and  hounds, 
putting  the  shot,  putting  the  hammer,  vaulting,  baseball, 
and  football.  In  their  season  come  boating  and  swim- 
ming, skating  and  coasting.  Suitable  for  both  boys  and 
girls  are  archery,  basket  ball,  bicycling,  croquet,  golf, 
horseback  riding,  tennis,  and  last,  but  not  least,  walking. 
The  main  trouble  with  walking  is  that  it  is  likely  to  be 
taken  from  a  sense  of  duty  and  becomes  mechanical. 
The  good  feature  of  most  games  is  that  there  is  active 
competition,  which  makes  them  so  enjoyable  that  one  en- 
tirely forgets  his  work  for  the  time.  He  is,  therefore,  in 
better  condition  to  return  to  his  work. 

Exercise  in  One's  Room.  —  In  one's  room  he  can  use 
dumb-bells  or  Indian  clubs  to  good  advantage.  There  are 


1 94  Physiology. 

also  various  forms  of  "  home  exercisers,"  such  as  pulley 
weights,  rubber  bands,  etc.,  which  are  valuable.  After 
exercise  should  come  a  sponge  bath. 

Games  of  School  Children.  —  Most  of  the  games  of  school 
children  are  excellent  kinds  of  exercise.  Cases  have  been 
reported  of  injury  from  excessive  skipping  the  rope ;  but 
in  moderate  degree  it  is  a  good  exercise.  Tag,  snowballing, 
racing,  the  various  games  of  ball,  jumping,  hopping,  and 
other  games  may  be  played  on  the  school  grounds. 

Tennis.  —  Tennis  is  a  fine  game  and  suitable  for  girls  as  well  as  boys. 
It  has  the  great  advantage  over  baseball  that  it  does  not  require  a  large 
ground.  Two  can  make-up  a  game, 'and  a  little  time  can  be  better  used 
than  with  the  games  requiring  more  players.  The  exercise,  too,  is  more 
evenly  distributed.  There  is  no  long  waiting,  as  in  some  games,  but  a 
constant  interchange  of  play,  active  but  not  severe,  with  almost  no  danger 
of  injury. 

Baseball  and  Football.  —  For  those  who  can  pursue  the  more  vigor- 
ous games  of  baseball  and  football  they  are  admirable.  All  these  games 
calling  for  great  activity  and  strength  develop  manly  qualities  in  boys, 
and  do  much  to  make  them  active,  fearless  men,  men  who  in  time  of 
danger  have  not  only  strength  and  endurance,  but  well-trained  muscles, 
cool  heads,  and  brave  hearts ;  men  who  know  what  to  do  and  how  to 
do  it  in  an  accident,  as  at  fires,  upsetting  of  boats,  etc.  A  few  strong, 
cool-headed  men,  by  their  presence  of  mind,  often  stop  a  panic  and  save 
many  lives  when  there  is  an  alarm  of  fire,  which  often  proves  false.  The 
Duke  of  Wellington  said  that  it  was  on  the  football  fields  of  Eton  and 
Rugby  that  the  battle  of  Waterloo  was  won. 

Boxing.  —  Boxing  is  a  splendid  exercise.  It  calls  into  play  nearly 
every  muscle  of  the  body.  Boxing  makes  one  quick  on  his  feet,  trains 
to  quick  movements  of  the  arms,  trains  the  eye,  keeps  the  body  in  an 
erect  position,  and  especially  develops  the  muscles  of  the  legs  and  back. 
Boxing  brings  out  the  chest  and  shoulders.  It  develops  the  "wind," 
and  keeps  one  in  constant  action.  It  teaches  control  of  the  temper 
more  than  almost  any  form  of  exercise.  It  develops  a  degree  of  self- 
reliance  that  is  worth  much.  Like  tennis,  boxing  calls  for  little  appa- 


Exercise  and  Bathing.  195 

ratus,  little  space,  and  only  two  persons.  In  many  places  where  ordinary 
gymnasium  work  is  out  of  the  question,  boxing  is  available.  It  is  indeed 
a  "  manly  art,"  and  the  doctrine  taught  in  Tom  Brown's  School  Days  at 
Rugby  is  as  wholesome  as  can  be  given  to  boys  to  make  them  strong  and 
active,  to  give  them  physical  and  moral  health. 

Bicycling.  —  This  is  an  excellent  exercise,  as  it  is  in  the  open  air  and 
exhilarating.  There  is  danger  of  over-exertion,  and  it  is  bad  for  one  to 
yield  to  the  temptation  to  make  long  runs.  There  is  danger  of  over- 
taxing the  heart.  The  handle  bar  should  be  adjusted  to  allow  a  fairly 
upright  position.  The  saddle  should  be  such  as  to  sustain  the  weight 
properly. 

"Taking  Cold. "  —  So  long  as  one  is  actively  exercising, 
he  is  not  likely  to  take  cold.  But  if  one  rests  in  a  cool 
place,  especially  when  he  is  warm,  he  is  likely  to  take  cold. 
The  application  of  cold  to  the  skin  causes  the  arteries 
(through  reflex  action)  to  become  smaller.  Thus  when  rest- 
ing in  a  cool  place  the  skin  becomes  pale  and  cold.  Dur- 
ing a  "  cold  "  there  is  fever.  The  regulation  of  the. heat  by 
the  skin  is  interfered  with.  Waste  matter  is  not  given  off 
by  the  skin  as  it  should  be.  At  the  same  time  it  is  often 
noticeable  that  the  urine  is  more  abundant  than  usual.  A 
cold  is  often  associated  with  constipation  and  inactivity  of 
the  liver,  indicating  a  clogged  condition  of  the  system.  As 
a  cold  may  lead  to  fatal  lung  disease,  so  it  may  be  the 
beginning  of  disease  of  the  kidneys  that  may,  in  the  end, 
bring  fatal  results. 

Bathing.  —  One  purpose  of  bathing  is  to  cleanse  the 
skin.  For  this  purpose  warm  water  is  best,  and  it  is  desir- 
able to  use  soap,  especially  on  those  parts  which  are  espe- 
cially exposed  to  contamination,  such  as  the  hands,  the 
feet,  the  armpits,  and  groins.  The  feet  should  be  bathed 
every  night 


196  Physiology. 

Cold  Baths.  —  Another  important  function  of  bathing  is 
to  strengthen  the  system.  For  this  purpose  cold  bathing 
is  better,  but  this  should  not  be  too  long  continued,  and 
must  be  followed  by  a  brisk  friction  to  give  the  skin  a  ruddy 
glow.  For  this  kind  of  bath  a  tub  is  not  necessary,  and 
hardly  desirable.  The  water  may  be  quickly  applied  by 
means  of  a  sponge,  or  bath  mits  made  of  Turkish  toweling, 
and  the  body  thoroughly  rubbed  with  a  coarse  towel.  The 
whole  process  should  be  completed  very  quickly,  especially 
if  the  room  is  not  warm.  At  the  beginning  of  a  bath,  cold 
water  should  be  applied  to  the  head  and  face. 

Time  for  Bathing.  —  For  those  who  do  not  take  a  great 
deal  of  vigorous  exercise,  which  keeps  the  skin  active, 
bathing  is  especially  valuable.  The  use  of  warm  water 
for  cleansing  seems  best  adapted  to  the  time  of  going  to 
bed.  But  the  best  time  for  the  cool  bath  is  on  getting  up 
in  the  morning. 

Warm  Baths  vs.  Cold  Baths.  —  Prolonged  warm  baths 
are  weakening,  and  probably  increase  a  tendency  to  take 
cold,  whereas  cold  bathing  is  one  of  the  very  best  means 
of  fortifying  against  cold,  and  especially  against  the  ten- 
dency to  take  cold  on  slight  exposure.  For  most  persons 
a  cool  sponge  bath,  on  rising,  will  act  as  a  most  excellent 
tonic ;  but  if  it  seems  to  produce  neuralgia,  it  should  be 
used  with  caution. 

Exercise  of  Arterial  Muscles.  —  We  have  learned  that 
the  blood  supply  to  any  organ  is  regulated  by  the  action 
of  the  plain  muscle  fibers  in  the  walls  of  the  small  arter- 
ies. Now,  when  we  are  subject  to  changes  in  temperature 
these  muscles  get  exercise,  and  one  writer  has  well  called 
the  cold  bath  the  gymnastics  of  the  plain  muscle  fibers, 


Exercise  and  Bathing.  197 

and  we  can  understand  how  the  system  can  be  trained  to 
adjust  itself  to  cold,  and  enabled  to  avoid  "taking  cold." 

Habit  of  Cold  Bathing  acquired  Gradually.  —  There  are 
undoubtedly  many  persons  who  do  not  profit  by  cold  bath- 
ing, but  probably  many  of  these  would  soon  adapt  them- 
selves to  it  by  beginning  with  tepid  water  and  gradually 
using  cooler.  To  bath  slowly  in  a  cold  room  is  not  safe. 
The  great  secret  of  the  benefit  that  may  be  expected  from 
a  cold  bath  is  to  be  very  brisk,  the  whole  process  occupying 
only  a  few  minutes.  Many  are  opposed  to  cold  sponge 
bathing,  and  condemn  it  without  giving  it  a  fair  trial. 

Summary.  —  i.  Exercise  stimulates  the  activity  of  all  the  organs,  by 
promoting  cell  activity  and  assisting  excretion. 

2.  Exercise  should  be  in  the  open  air  as  much  as  possible. 

3.  Exercise  is  more  beneficial  when  it  exhilarates. 

4.  Exercise  should  be  taken  regularly. 

5.  Warm  baths  are  best  for  cleansing,  and  should  be  taken  at  bed- 
time. 

6.  Cold  baths  stimulate  the  circulation  of  blood  in  the  skin,  and 
serve  as  a  tonic  to  the  whole  system.     Just  after  rising  is  a  good  time 
for  the  cold  bath. 

7.  The  cold  bath  fortifies  against  taking  cold. 

Questions.  —  i.   Should  exercise  be  carried  to  the  point  of  fatigue  ? 

2.  How  can  one  avoid  taking  cold  after  exercise  ? 

3.  Do  girls  need  exercise  as  much  as  boys  ? 

4.  What  is  the  condition  of  the  body  during  a  "  cold"  ? 

5.  How  may  a  cold  be  caused  ? 

6.  How  may  a  cold  be  cured  ? 

7.  How  may  a  cold  be  prevented  ? 

8.  Why  do  some  persons  take  cold  more  readily  than  others  ? 

9.  Why  does  the  same  person  take  cold  more  readily  at  one  time 
than  at  another  ? 

TO.  How  often  should  a  person  bathe  ? 

1 1 .   What  hour  is  best  for  sea  bathing  ?     Why  ? 


CHAPTER   XXI. 
THE  BRAIN. 

The  Coverings  of  the  Brain.  — There  are  two  coats  of 

the  brain,  the  dura  mater,  a  tough  membrane,  adhering  to 
the  inside  of  the  skull;  and  the  pia  mater,  next  to  the 
brain,  a  much  thinner  membrane,  traversed  by  blood 
tubes,  and  dipping  down  into  the  grooves  between  the 
convolutions  of  the  cerebrum. 

The  Parts  of  the  Brain.  —  The  parts  of  the  brain  are  the 
cerebrum,  the  cerebellum,  and  the  spinal  bulb. 

The  Cerebrum.  —  The  cerebrum  consists  of  two  lateral 
hemispheres,  separated  by  a  deep  groove  in  the  middle 
line.  The  surface  of  the  cerebrum  is  in  irregular  ridges, 
the  convolutions.  The  outside  of  the  brain  consists  of 
gray  matter.  The  inner  part  of  the  brain  is  white,  and 
the  two  halves  are  connected  by  a  broad  band  which  con- 
sists of  many  white  fibers. 

The  Cerebellum.  —  Back  of,  and  below  the  cerebrum  is 
the  cerebellum.  It  is  much  smaller  than  the  cerebrum, 
and  has  fine  transverse  ridges  and  grooves  in  place  of  the 
convolutions  of  the  cerebrum.  It  is  also  of  a  deeper  color, 
a  reddish  gray. 

The  Spinal  Bulb.  —  The  enlarged  beginning  of  the 
spinal  cord  is  the  spinal  bulb.  It  is  white,  like  the  rest  of 
the  cord. 

198 


The  Brain. 


199 


The  Cranial  Nerves  and  their  Functions.  —  i.  The 
olfactory  lobes  extend  forward  under  the  fore  part  of  the 
cerebral  hemispheres.  They  are  the  nerves  of  smell. 


—    I,  Olfactory 
(Smell) 


Eye  Motor, 
3,4,6 


Hypoglossal, 
12  (Tongue 
Motor) 


II,  Spinal 
Accessory 


Fig.  88.    The  Base  of  the  Brain,  showing  the  Origin  of  the  Cranial  Nerves. 

2.  The  optic  nerves,  or  nerves  of  sight,  join  each  other 
before  reaching  the  brain. 

3.  The  third  pair  of  cranial  nerves  controls  part  of  the  muscles  of 
the  eyeballs. 

4.  The  fourth  pair  also  controls  eye  muscles. 

5.  Back  of  these  is  the  larger  fifth  pair,  the  trigeminal. 
This  pair  supplies  part  of  the  face,  and  sends  branches  to 


200  Physiology. 

the  teeth.     It  is  the  nerve  affected  in  neuralgia  of  the  face. 
It  is  the  nerve  of  sensation  for  most  of  the  head  and  face. 

6.  The  sixth  pair  controls  eye  muscles. 

7.  The  seventh  pair  are  larger,  and  are  farther  back 
and  outward.     These  are  the  facial  nerves,  and  control  the 
muscles  of  the  face  and  the  facial  expression. 

Cerebrum 


Spinal  Bulb 


Fig.  89.     Vertical  Section  of  Brain. 

8.  The  eighth,  or  auditory  nerves,  are  the  nerves  of 
hearing. 

9.  The  ninth  pair  arise  on  the  sides  of  the  spinal  bulb. 
They  supply  the  back  of  the  tongue  and  the  pharynx,  and 
are  called  the  glosso-pharyngeal  nerves.     They  give  the 
sense  of  taste  from  the  base  of  the  tongue. 

10.    The  tenth  pair,  or  vagus  nerves,  pass  down  out  of 
the  brain  cavity,  give  off  branches  to  the  pharynx  and 


The  Brain. 


201 


larynx,   and    are    distributed    to    the    heart,    lungs,    and 
stomach. 

11.  The  eleventh  pair  arise  in  part  from  the  spinal  cord  outside  of 
the  cranial  cavity,  enter  the  skull,  and  pass  out  again  to  supply  certain 
muscles  of  the  neck  and  shoulders. 

12.  The  last  pair  of  cranial  nerves,  the  twelfth,  supplies  the  muscles 
of  the  tongue,  and  are  called  the  hypoglossal  nerves. 

Gray  and  White  Matter  of  the  Brain. 

—  The  gray  matter  of  the  brain  is  com- 
posed of  cells  similar  to  those  of  the 
spinal  cord,  while  the  white  matter 
of  the  inner  part  is  composed  of  white 
fibers  like  those  of  the  outer  part  of 
the  spinal  cord,  or  of  the  nerves. 

Ganglions  of  the  Brain.  —  There  are  several  masses  of 
gray  matter  in  the  interior  of  the  brain.  These  are  the 

ganglions      Of     the  _^^^A  ^  Gray  Matter 

brain.  The  white 
fibers  inside  the 
brain  connect  the 
gray  matter  of 
the  convolutions 
and  these  gang- 
lions with  all  parts 
of  the  body 
through  the  spinal 
cord. 

Functions  of  the  Cerebrum.  —  The  gray  matter  of  the 
outside  of  the  brain  is  the  central  organ  of  intelligent  sen- 
sation and  motion.  The  functions  of  volition,  or  willing, 
of  consciousness,  of  intelligence,  seem  to  reside  in,  or  rather 
to  depend  upon  the  activities  of,  the  cells  of  the  gray 
matter  of  the  convolutions  of  the  cerebrum. 

14 — PHY 


Ganglions 


Fig.  91. 


Cerebrum 


Cerebellum 


Diagram  of  the  Brain,  showing  the  Spinal  Cord, 
Ganglions,  and  Course  of  the  Fibers. 


202 


Physiology. 


The  Center  of  Sensations  itself  Insensible. — All  sensation 
seems  to  be  in  the  gray  matter  of  the  convolutions  of  the 
cerebrum,  and  yet  it  is  itself  insensible ;  it  may  be  cut  and 
cause  no  sensation.  But  when  the  nerve  impulses  from  the 
various  parts  of  the  body  reach  the  gray  matter  of  the  cere- 


Face  Sensory 

Face  Motions 

Taste 


Spinal  Cord 
1st  Spinal  Nerve 
2d  Spinal  Nerve 


Fig.  92.    The  Cranial  Nerves  and  Sense  Organs. 


brum  they  rouse  the  cells  here  to  an  activity  that  gives  us 
what  we  call  sensation.  It  is  never  a  sensation  until  it 
reaches  this  part  and  is  properly  interpreted. 

Crossed  Control  of  the  Body.  —  While  each  hemisphere 
mainly  controls  the  muscles  of  the  opposite  half  of  the 
body,  it  also,  in  part,  has  control  of  its  own  side.  Paralysis 


The  Brain. 


203 


of  one  side  is  due  to  injury  of  the  opposite  hemisphere  of 
the  cerebrum. 

Location  of  Brain  Functions.  —  Much  has  been  learned  in 
late  years  as  to  the  location  of  special  functions  in  the  brain. 


CENTRAL  FISSURE 


MOTOR  AREA  / 


FISSURE  OF  SILVIUS 


Fig.  93.    Location  of  Brain  Functions. 

Some  of  the  motor  and   sensory  centers   are   shown  in 
Fig.  93- 

Connection  of  Brain  Centers. — These  different  brain 
centers  are  connected  by  nerve  fibers,  and  through  these 
connecting  fibers  we  produce  various  actions  as  a  result  of 
sensations.  For  instance  (see  Fig.  94),  nerve  impulses  come 
through  the  nerve  of  hearing  to  the  auditory  center,  and  we 
have  hearing;  this  center  is  connected  with  the  speech 
center ;  and,  as  a  result,  we  send  out  nerve  currents  to  the 


204 


Physiology. 


organs  of  speech,  and  thus  we  speak  in  response  to  what 
we  hear.  Currents  from  the  eye  reaching  the  visual  center 
may  connect  with  the  writing  center,  and  we  send  out  cur- 
rents by  which  we  write  in  response  to  what  we  have  read. 

Writing 


Speech 


Auditory 


Fig.  94.    Connection  of  Brain  Centers.     (After  Landois  and  Stirling.) 

Left  Hemisphere  Better  Developed.  —  The  "  speech  cen- 
ter" is  in  the  left  hemisphere;  the  right  eye  and  ear,  which 
connect  with  the  left  brain,  are  better  developed  than  the 
left,  and  in  general  the  left  hemisphere  seems  superior  (in 
right-handed  persons)  to  the  right. 

The  Function  of  the  Cerebellum.  —  The  cerebellum  is  the 
center  for  regulating  the  actions  of  the  skeletal  muscles. 


The  Brain.  205 

When  we  walk  or  run,  or  even  stand  still,  a  number  of 
muscles  must  act,  and  act  in  concert.  The  nerve  impulses 
originate  in  the  cerebrum,  but  the  cerebellum  is  the  center 
for  harmonizing  the  action  of  these  various  muscles.  When 
the  cerebellum  is  injured,  an  animal  staggers  instead  of 
walking  steadily. 

Functions  of  the  Spinal  Bulb.  —  The  spinal  bulb  is  the 
enlarged  part  of  the  spinal  cord  which  is  within  the  cra- 
nium. From  it  arise  all  the  cranial  nerves  except  the  first 
five  pairs.  The  spinal  bulb  is  also  the  center  for  the  con- 
trol of  respiration,  of  circulation,  of  swallowing,  and  perhaps 
for  many  other  processes. 

Brain  Work  and  Brain  Rest  —  Sleep  is  not  merely  rest 
for  the  body  ;  it  should  be  complete  rest  for  the  brain.  In 
so  far  as  there  are  dreams,  it  would  seem  to  indicate  a  par- 
tial activity  ;  that  is,  incomplete  rest.  The  brain,  like  the 
muscles,  needs  exercise,  and  it  also  needs  regular  periods 
of  rest.  If  a  nerve  cell  is  not  kept  active  by  the  passage 
of  nerve  impulses  through  it,  it  usually  dwindles  away, 
and  may  entirely  lose  its  power. 

Sleeplessness.  —  Intense  brain  work,  without  sufficient 
sleep,  is  likely  to  lead  to  sleeplessness,  as  when  one  has 
some  subject  of  special  study  in  hand  and  either  will  not 
or  cannot  throw  it  off.  Perhaps  inventors  are  as  subject 
to  this  sort  of  trouble  as  any  one  class  of  men.  Keeping 
the  blood  continually  in  the  brain  is  likely  to  lead  to  a  per- 
manent congestion,  or  inflammation,  that  may  cause  seri- 
ous, if  not  fatal,  results. 

Fatigue.  —  It  is  stated  that  brain  workers  need  more 
sleep  than  those  who  work  chiefly  with  the  muscles.  Fa- 
tigue of  the  voluntary  muscles  is  much  more  a  matter  of 


206  Physiology. 

nervous  than  of  muscular  origin.  When  one  is  completely 
"tired  out,"  as  he  would  say,  if  his  mind  can  be  aroused, 
as  by  some  excitement,  he  will  be  found  able  to  expend  a 
good  deal  more  muscular  energy.  So,  too,  many  persons 
of  slight  muscular  build,  but  of  great  "  will  power,"  are 
able  to  do  more  work  with  the  muscles  than  others  with 
larger  muscles  and  less  will.  During  fatigue  the  cell 
bodies  are  found  to  decrease  in  size,  but  there  is  no  per- 
ceptible change  in  nerve  fibers  as  a  result  of  fatigue. 

Blood  Supply  of  the  Brain.  —  Blood  is  supplied  to  the 
brain  through  four  arteries :  the  right  and  left  internal 
carotid  arteries,  and  the  right  and  left  vertebral  arteries. 
These  arteries  are  so  connected  by  cross-branches  that  if 
any  three  of  them  should  be  compressed,  or  the  blood 
flow  in  them  otherwise  stopped,  the  fourth  would  still  be 
able  to  give  the  brain  blood  enough  for  its  work.  When 
the  brain  is  more  active  it  receives  a  larger  supply  of 
blood.  During  sleep  it  is  paler. 

Cause  of  Fainting. — If  the  supply  of  blood  to  the  brain 
is  shut  off,  unconsciousness  quickly  follows.  In  the  ordi- 
nary faint  the  blood  supply  to  the  brain  has  been  reduced. 
It  is  due  to  checking  the  action  of  the  heart  from  some 
emotion,  or  bad  air,  as  in  a  close  room ;  severe  pain  may 
be  the  cause ;  a  blow  over  the  pit  of  the  stomach  may  stop 
the  heart  by  reflex  action. 

Apoplexy.  —  Apoplexy  is  caused  by  rupture  of  a  blood 
tube  and  the  formation  of  a  clot  that  presses  on  the  brain. 

Meningitis.  —  Meningitis  is  an  inflammation  of  the  mem- 
branes immediately  surrounding  the  brain  or  spinal  cord 
or  both. 


The  Brain.  207 

Summary.  —  I .  The  outside  of  the  brain  consists  of  gray  matter,  the 
inside  of  white  matter. 

2.  The  twelve  pairs  of  cranial  nerves  are  distributed  to  the  head,  with 
the  exception  of  the  tenth  and  part  of  the  eleventh. 

3.  The  cranial  nerves  include  the  senses  of  sight,  smell,  taste,  and 
hearing. 

4.  Each  hemisphere  of  the  brain  is  connected  with,  and  has  chief 
control  of,  the  opposite  half  of  the  body. 

5.  The  gray  matter  of  the  cerebrum  is  the  seat  of  the  will,  sensation, 
thought,  and  emotion. 

6.  The  cerebellum  regulates  voluntary  motion. 

7.  Many  of  the  cerebral  functions  have  been  located. 

8.  The  brain  needs  rest.     In  sleep  less  blood  flows  through  the 
brain. 

9.  Work  reduces  the  size  of  nerve  cells.     During  rest  they  increase 
again. 

Questions.  —  i.  Is  there  any  special  reason  why  the  "speech  center" 
should  be  in  the  left  cerebral  hemisphere  ? 

2.  Why  does  a  light  lunch  sometimes  enable  one  to  go  to  sleep  after 
mental  work  ? 

3.  Why  is  it  uncomfortable  to  hold  the  head  down  ? 

4.  How  does  the  nervous  system  resemble  a  telegraph  system  ?    In 
what  respects  are  the  two  unlike  ? 

5.  Name  some  remedies  for  sleeplessness. 


CHAPTER   XXII. 
THE    SENSES. 

THE  GENERAL  SENSES.  —  TOUCH    AND    TEMPERATURE 

SENSE. 

Afferent  and  Efferent  Nerve  Currents.  —  Up  to  this  point 
we  have  been  studying  efferent,  or  out-going,  nerve  cur- 
rents, such  as  control  muscles  and  glands.  Now  let  us 
turn  to  the  in-coming,  or  afferent,  currents ;  for  it  is  by 
means  of  the  afferent  currents  to  the  brain  that  we  get  all 
our  sensations.  In  other  words,  it  is  through  these  cur- 
rents that  we  get  all  our  knowledge. 

Two  Classes  of  Sensations.  —  There  are  two  classes  of 
sensations,  the  special  and  the  general.  The  special  senses 
include  sight,  hearing,  taste,  smell,  touch,  and  temperature 
sense.  Among  the  general  sensations  are  hunger,  thirst, 
fatigue,  nausea,  satiety,  faintness,  pain,  muscular  sense,  etc. 

Special  Sensation  due  to  External  Force.  —  Sensations 
from  the  organs  of  special  sense  are  due  to  the  action  of 
an  external  force.  For  instance,  sound  waves  entering  the 
ear  affect  the  nerves  of  hearing,  and  we  have  a  sensation 
of  hearing.  Light  acting  on  the  optic  nerve  gives  sight. 

General  Sensations  due  to  Conditions  within  the  Body. 

-There  are  nerves  of  general  sensibility  in  all  parts  of 

the  body.     The  endings  of  these  nerves  are  acted  on  by  the 

blood  and  lymph.     Currents  are  all  the  time  coming  through 

208 


The  Senses.  209 

these  nerves  to  the  brain.  But  ordinarily  we  are  not  con- 
scious of  them.  If  the  body  is  in  need  of  food,  the  mes- 
sages are  stronger  and  we  have  a  sensation  of  hunger.  If 
the  poisonous  waste  matters  are  not  removed  by  the  organs 
of  excretion,  their  presence  in  the  lymph  is  reported  to  the 
brain,  and  we  have  a  feeling,  perhaps  of  fatigue,  or  of 
decided  discomfort,  or  even  of  pain. 

The  Muscular  Sense.  —  In  judging  the  weight  of  a  body 
by  holding  it  in  the  hand,  our  estimate  is  the  result  of  sen- 
sations aroused  by  nerve  impulses  from  the  organs  used. 
There  are  afferent  nerve  fibers  with  endings  in  ( I )  the  skin, 
(2)  the  muscles  and  tendons,  and  (3)  the  joints.  In  hold- 
ing out  the  arm  and  in  moving  it  up  and  down,  all  three 
of  these  sets  of  nerve  endings  are  stimulated,  and  impulses 
are  conveyed  to  the  brain  producing  the  muscular  sense. 

Dependence  of  Sight  on  Muscular  Sense  and  Touch.  —  It  is  difficult  to 
realize  the  importance  of  the  muscular  sense.  An  illustration  of  the  as- 
sistance which  touch  and  the  muscular  sense  give  to  the  sense  of  sight 
is  furnished  in  the  case  of  a  boy  who  had  been  blind  from  birth,  and  re- 
ceived sight  at  the  age  of  twelve  years  by  means  of  a  surgical  operation. 
At  first  he  could  not  distinguish  a  globe  from  a  circular  card  of  the  same 
color  until  he  had  touched  them.  He  knew  the  peculiar  features  of  the 
dog  and  the  cat  by  feeling,  but  not  by  sight.  Happening  one  day  to 
pick  up  the  cat,  he  recognized  for  the  first  time  the  connection  between 
the  new  sense  of  sight  and  the  old  familiar  ones  of  touch  and  the  mus- 
cular sense.  On  putting  the  cat  down  he  said,  "  §o,  puss,  I  shall  know 
you  next  time." 

Pain.  —  The  nerves  of  general  sensibility  give  informa- 
tion of  the  state  of  nutrition  in  the  tissues  and  the  condi- 
tion of  the  body  as  a  whole.  Ordinarily  we  are  not  aware 
of  these  nerve  currents.  When  they  become  stronger 
than  usual  they  give  rise  to  feelings  of  general  discomfort, 
such  as  fatigue,  depression,  restlessness,  etc.  When  the 
currents  become  stronger  still,  we  have  pain. 


2 1  o  Physiology. 

Use  of  Pain.  —  Pain  is  a  warning  of  over-use  or  injury. 
The  milder  nerve  impulses  that  cause  slight  discomfort 
ought  to  be  sufficient  to  call  attention  to  the  condition.  But 
often  these  first  reports  are  neglected.  For  instance,  over- 
use or  abuse  of  the  eyes  may  cause  irritation,  that  is  allowed 
to  go  unheeded.  The  person  may  show  the  effect,  by  rub- 
bing the  eye,  but,  being  absorbed  in  study,  may  fail  to 
stop  reading  and  go  on  until  there  is  actual  pain.  When 
the  first  warnings  are  not  heeded,  pain  follows  and  demands 
attention. 

Pain  in  the  Skin.  —  While  the  internal  organs  are  ordina- 
rily without  feeling,  the  skin  is  especially  sensitive.  The 
skin  senses  stand  guard  at  the  outposts  of  the  body's 
camp,  and  give  warning  of  approaching  danger.  No 
enemy  may  enter  without  being  discovered  by  these  keen 
sentinels,  and  the  alarm  is  given.  In  amputating  a  limb 
the  chief  pain  is  in  cutting  through  the  skin.  It  is  a  com- 
fort to  know  that  the  more  severe  wounds  do  not  cause 
pain  in  proportion  to  their  extent 

Hunger  and  Thirst.  —  The  cause  of  these  sensations  in 
a  healthy  body  is  plainly  the  need  of  food  and  water 
throughout  the  system.  The  sensation  of  thirst  seems  to 
be  in  the  throat,  and  the  longing  may  be  somewhat  re- 
lieved by  merely  moistening  the  throat.  So  hunger  may, 
for  the  time,  be  appeased  by  filling  the  stomach  with  indi- 
gestible material.  But  the  sensation  soon  returns.  The 
system  has  a  crying  need,  and  it  is  not  to  be  put  off. 
That  these  sensations  are  really  demands  made  by  the 
body  as  a  whole  may  be  shown  by  the  fact  that  they  are 
permanently  relieved  by  introducing  food  and  water  into 
the  body  (by  the  rectum,  for  instance),  in  which  case  the 
throat  and  stomach  have  nothing  given  them  directly. 


The  Senses. 


211 


Since,  however,  food  and  drink  naturally  enter  by  the 
throat  and  stomach,  the  mucous  membrane  of  these 
organs  has  become  the  spokesman  of  the  body. 

What  we  learn  by  touching  Objects.  —  Let  one  person 
rest  the  hand  flat  on  the  table,  palm  upward,  and  close  the 
eyes.     An   object   placed   on   the 
palm,  by  another  person,  may  give 
rise  to  various  sensations,  so  that 
it  may  be  described  as  rough  or 
smooth,    light    or    heavy,   hot    or 
cold,  wet  or  dry,  etc.      If  now  the 
thumb  and  fingers  are  raised  and 
applied  to  the  object,  more  definite 
information  will  be  gained  as  to  its 
shape,    size,    surface,    etc.      Now 
raise  the  object  in  the  hand,  and 
further  appreciation  will  be  gained 
as   to  its  weight.      These  experi- 
ments show  that  several  sensations  are  involved  in  the 
handling  of  objects,  and  that  the  knowledge  so  gained  is 
complex. 

Cutaneous  Sensations.  —  The  sensations  from  objects 
resting  on  the  skin  of  the  hand  may  all  be  referred  to  im- 
pressions made  on  nerve  endings  in  the  skin,  and  are 
called  cutaneous  sensations.  They  include  :  ( I )  the  pres- 
sure sense,  or  touch  proper,  (2)  the  temperature  sense,  and 
(3)  pain. 

Nerve  Endings  in  the  Skin.  —  The  skin  consists  of  two 
layers,  the  epidermis  and  the  dermis  (see  Figs.  64  and  65). 
In  the  papillas  of  the  dermis  are  nerve  endings  called 
touch  corpuscles  (see  Fig.  95). 


Nerve 

Fig.  95.     Papilla  of  Skin  with 
Touch  Corpuscle. 


212  Physiology. 

Pressure  on  the  skin  affects  these  nerve  endings,  and 
starts  impulses  that  pass  along  the  sensor  fibers,  through 
the  spinal  cord,  to  the  brain,  and  give  us  sensations  of 
touch.  If  a  nerve  fiber  is  touched,  not  at  the  end,  but 
somewhere  along  its  course,  we  get  a  sensation,  not  of 
touch,  but  of  pain. 

The  Sense  of  Touch,  —  Of  the  special  senses  the  most 
general  is  that  of  touch.  Seeing  and  hearing,  taste  and 
smell,  belong  to  very  limited  parts  of  the  outside  of  the 
body,  but  we  have  the  power  of  feeling  all  over  the  surface 
of  the  body.  Except  in  the  mouth  and  nose,  we  get  little, 
if  any,  sense  of  touch  from  any  organ  but  the  skin.  The 
lining  of  the  digestive  tube  and  the  internal  organs  gener- 
ally lack  this  sense. 

The  Pressure  Sense.  —  The  sense  of  touch,  proper,  is 
strictly  a  pressure  sense.  If  we  test  the  skin  to  find  what 
regions  are  able  to  detect  the  least  pressure,  it  is  found 
that  the  forehead  is  most  sensitive,  and  nearly  equally  so 
are  the  temples,  back  of  the  hand,  and  forearm. 

Location  of  Touch  Sensations.  —  Each  small  spot  of  skin 
has  its  own  nerve  endings  and  each  nerve  fiber  connects 
with  a  particular  part  of  the  gray  matter  of  the  brain.  The 
brain  can  therefore  tell  where  each  nerve  current  came 
from,  and  thus  we  locate  a  sensation. 

Accuracy  in  locating  Touch  Sensations.  —  The  accuracy 
varies,  and  is  ordinarily  keenest  where  the  nerves  are  most 
numerous.  Where  the  sense  of  locality  seems  to  be  im- 
proved by  cultivation,  this  appears  to  be  due  to  keener  per- 
ception in  the  brain  cells,  and  not  to  changes  in  the  nerves 
or  nerve  endings.  This  is  shown  in  the  fact  that  if  the 
fingers  of  one  hand  become  more  skilled  in  touch  by  prac- 


The  Senses.  213 

tice,  it  will  be  found  that  the  fingers  of  the  other  hand, 
without  special  training,  are  also  improved. 

Test  by  Compass  Points.  —  The  delicacy  of  localizing 
touch  is  usually  tested  in  this  way.  The  blunted  points  of 
a  light  pair  of  compasses  are  allowed  to  rest  gently  on  the 
skin  of  various  parts  of  the  body.  If  the  two  points  are 
very  close  together,  they  will  befe/t  as  one  pressure.  That 
part  which  can  best  distinguish,  as  two  points  of  touch, 
these  blunt  points,  is  considered  the  most  sensitive.  By 
this  test  the  tip  of  the  tongue  is  the  most  sensitive,  being 
able  to  distinguish,  as  two  separate  points  of  contact,  the 
tips  of  the  compasses  when  only  one  twenty-fifth  part  of 
an  inch  apart.  Following  is  the  order  of  degrees  of  sensi- 
tiveness :  tip  of  tongue,  tips  of  fingers,  lip,  tip  of  nose,  eye- 
lid, cheek,  forehead,  knee,  neck ;  while  the  middle  of  the 
back  seems  least  sensitive. 

Reference  of  Sensation  to  the  Region  of  Nerve  Endings.  — 
If  the  "  funny  bone,"  or  "  crazy  bone,"  be  hit,  i.e.  if  the 
ulnar  nerve  be  bruised  against  the  bone,  sharp  pain  may 
be  felt  in  the  wrist  and  hand,  and  soreness  of  these  parts 
may  be  felt  for  days,  though  they  are  not  in  the  least 
injured,  but  only  the  nerve  at  the  elbow.  The  currents 
along  this  nerve  rouse  sensations  that  we  have  learned  to 
locate  at  the  endings  of  the  nerve  fibers.  If,  then,  owing 
to  injury,  the  currents  start  from  the  elbow,  the  brain  still 
refers  them  to  the  nerve  endings  in  the  hand  and  wrist. 
So,  too,  after  amputation  of  a  hand  or  foot,  there  may 
for  years  be  sensations  referred  to  the  missing  member, 
probably  due  to  irritation  of  the  nerves  of  the  stump. 

The  Temperature  Sense.  —  Many  cases  are  on  record  in 
which,  from  accident  or  disease,  the  sense  of  touch  was 
lost  and  the  temperature  sense  retained,  or  vice  versa. 


214  Physiology. 

Such  facts  have  led  to  the  belief  that  the  temperature 
sense  is  distinct  from  that  of  touch,  and  has  its  own  nerve 
fibers  and  nerve  endings. 

Summary.  —  i .  The  special  senses  result  from  the  action  of  external 
forces,  such  as  light,  heat,  etc. 

2.  General  sensations  are  referred  to  our  bodies  and  their  condition. 

3.  The  muscular  sense  depends  on  impulses  from  muscles,  tendons, 
and  joints. 

4.  The  muscular  sense  and  touch  aid  the  sense  of  sight  in  giving  us 
correct  perceptions  of  size  and  form. 

5.  Pain  is  a  general  sensation.     It  is  a  warning  —  the  cry  of  a  senti- 
nel that  an  enemy  has  passed  the  picket  line. 

6.  Hunger  and  thirst  indicate  the  need  of  food  and  drink.     They 
are  local  signals  of  a  general  want. 

7.  The  cutaneous  sensations  are  touch,  temperature  sense,  and  pain. 

8.  There  are  touch  corpuscles  in  the  papillas  of  the  dermis. 

9.  Touch  is  the  most  general  of  the  senses. 

10.  Touch  proper,  or  pressure  sense,  is  tested  by  perception  of  pres- 
sure. 

11.  Touch  localization  is  tested  by  discrimination  as  to  the  distance 
of  two  points  of  contact. 

12.  Temperature  is  discerned  by  a  special  set  of  nerve  fibers. 

13.  Sensations  are  referred  to  the  region  of  the  nerve  endings. 

Questions.  —  i.    What  is  the  explanation  of  tickling. 

2.  Where  does  the  change  occur  by  which  we  become  more  skilled 
in  the  sense  of  touch  ? 

3.  Why  does  an  emotion,  such  as  shame,  make  one  feel  hot  ? 

4.  If  we  had  no  sense  of  pain,  what  might  result  ? 

5.  If  we  pass  by  a  meal  time  without  eating  why  does  the  sense  of 
hunger  usually  disappear  ? 


CHAPTER   XXIII. 
THE  SENSE  OF  SIGHT. 

Protection  of  the  Eye.  —  The  eye  is  set  well  back  in  its 
socket  and  guarded  by  three  bony  projections,  —  the  brow, 
cheek  bone,  and  the  bridge  of  the  nose.  It  is  further 
protected  by  the  eyelids  and  eyelashes. 

The  Lacrymal  Secretion.  —  The  lacrymal  gland,  or  tear 
gland,  is  just  above  the  outer  angle  of  the  eye,  and  pours 
its  secretion  over  the  eyeball.  The  lids  serve  as  curtains 
to  admit  or  shut  out  light,  and,  by  winking,  wash  the  eye. 
It  is  as  though  a  man  were  kept  all  the  time  in  front  of  a 
plate-glass  window,  with  water  and  rubber  scraper,  to  keep 
it  clean  and  bright.  The  lacrymal  secretion  is  ordinarily 
carried  off  into  the  nasal  cavity  as  fast  as  it  is  made.  If 
the  ducts  are  stopped,  or  if  the  secretion  is  formed  very 
rapidly,  the  liquid  overflows  on  the  face  as  tears. 

The  External  Parts  of  the  Eye. — The  "white  of  the 
eye  "  is  the  sclerotic  coat.  It  has  blood  tubes,  but  ordina- 
rily they  are  not  conspicuous.  The  front  part  of  the  eye- 
ball is  covered  with  the  cornea.  This  is  transparent,  and 
the  color  of  the  iris  shows  through  the  cornea.  In  the 
center  of  the  iris  is  the  hole,  or  pupil,  by  which  light  enters 
the  interior  of  the  eye. 

The  Conjunctiva.  —  The  front  of  the  eyeball  is  covered 
by  a  thin,  transparent,  mucous  membrane,  the  conjunctiva, 
which  turns  back  and  lines  the  inside  of  the  eyelids.  It  is 
very  sensitive. 

215 


2l6 


Physiology. 


Movements  of  the  Eye.  —  There  are  six  pairs  of  muscles  which  move 
the  eyes  to  right  and  left,  up  and  down,  and  give  rotary  movements. 
The  two  eyes  move  in  the  same  direction  at  the  same  time,  though  in 
looking  at  near  objects  the  two  eyes  both  point  inward,  so  that  one 
appears  cross-eyed. 

Dissection  of  an  Eye.  —  The  muscles  and  external  parts  of  the  eye 
may  readily  be  seen  by  examining  the  eye  of  a  rabbit  in  its  natural 
position  and  then  dissecting  it  out.  A  beef  eye  should  be  obtained 
from  the  butcher  and  the  structure  of  the  eye  learned  by  following  the 
description. 

Ciliary  Muscle 


Optic  Nerve  Choroid 

Fig.  96.    Horizontal  Section  of  Right  Eye. 

The  Coats  of  the  Eye.  —  There  are  three  coats,  the  outer 
or  sclerotic,  the  middle  or  choroid,  and  the  inner  or  retina. 

The  Sclerotic  Coat.  —  This  is  of  a  dull  white  color,  con- 
stituting the  "white  of  the  eye."  It  is  thick  and  tough, 
holding  all  the  contained  parts  firmly  and  furnishing  suffi- 
cient strength  for  the  attachment  of  the  muscles  that  move 
the  eyeball. 


The  Sense  of  Sight.  217 

The  Choroid  Coat.  —  The  middle  coat  of  the  eye  is  the 
choroid.  It  is  thinner  than  the  sclerotic  and  of  much  more 
delicate  structure.  It  is  full  of  blood  tubes,  and  has  an 
inner  lining  of  dark  color  to  prevent  the  reflection  of  light 
in  the  eye,  just  as  most  optical  instruments  are  painted 
black  on  the  inside. 

The  Retina.  —  The  retina  is  an  expanded  part  of  the 
optic  nerve  and  forms  an  inner  coat  that  lines  all  but  the 
front  part  of  the  eye.  It  is  a  thin,  translucent  film,  some- 
what like  the  film  that  iorms  over  the  white  of  an  egg  when 
it  is  first  dropped  into  hot  water.  It  is  very  delicate  and 
easily  torn.  The  retina  is  the  only  part  of  the  eye  that  is 
sensitive  to  light,  and  on  it  the  images  must  be  formed  to 
produce  distinct  vision. 

The  Cornea.  —  The  clear  front  part  of  the  eye  is  the 
cornea.  It  is  a  continuation  of  the  sclerotic  coat  and  is 
more  bulging  than  the  rest  of  the  front  of  the  eye,  as  can 
be  seen  by  taking  a  side  view  of  the  eye,  or  by  noticing 
some  one  who  closes  the  eyelids  and  rolls  the  eyes  about. 

The  Iris.  —  This  is  the  part  that  gives  the  color  to  the 
eye,  or  if  the  pigment  that  gives  the  color  is  lacking,  the 
blood  gives  the  pink  color  seen  in  albinos.  The  iris  is  a 
forward  continuation  of  the  choroid  coat. 

The  Pupil.  —  Most  of  the  light  that  passes  through  the 
transparent  cornea  is  stopped  by  the  opaque  iris.  But  in 
the  center  of  the  iris  is  a  round  hole  through  which  light 
enters  the  interior  of  the  eye.  The  pupil  looks  dark  be- 
cause it  is  the  only  opening  into  a  dark  room. 

Regulation  of    the  Amount  of    Light   admitted  into  the    Eye. — 
Hold  a  hand  glass  between  the  face  and  a  well-lighted  window.     Note 
the  size  of  the  pupils.     Quickly  turn  toward  the  darkest  part  of  the 
15 — PHY 


2 1 8  Physiology. 

room.  The  iris  has  circular  muscle  fibers  that  make  the  pupil  smaller 
when  there  is  too  much  light  for  the  eye,  and  when  the  light  is  feeble 
the  pupil  opens  wider. 

The  Aqueous  Humor.  —  There  is  a  small  space  between 
the  cornea  and  the  iris.  In  this  space  is  the  clear,  watery 
aqueous  humor. 

The  Vitreous  Humor.  —  All  but  the  front  part  of  the 
space  within  the  eye  is  filled  with  a  clear,  jelly-like  sub- 
stance, the  vitreous  humor. 


Fig.  97.    The  Formation  of  an  Image  on  the  Retina. 

The  Crystalline  Lens. — Just  back  of  the  iris  is  a  double- 
convex  lens,  clear  as  crystal,  and  of  about  the  consistency 
of  a  gumdrop.  It  is  less  convex  on  the  front  surface. 

Experiment  with  Lens  to  show  Inversion  of  Image.  —  Take  a 
double-convex  lens  or  any  hand  magnifier.  Hold  this  up  at  the  rear 
of  the  room  and  catch  the  inverted  image  of  the  window  on  a  piece  of 
paper  held  back  of  the  lens.  This  illustrates  how  the  image  of  an 
external  object  is  formed  by  the  crystalline  lens  upon  the  retina  of 
the  eye. 

Experiments  to  illustrate  the  Adjustment  for  Distance.  —  (0  Stick 
a  pin  at  each  end  of  a  book  cover.  Hold  the  book  at  about  the  usual 
distance  for  reading,  so  that  the  two  pins  are  in  a  line  with  the  eye. 
Look  closely  at  the  nearer  pin,  and  the  second  pin  will  appear  indistinct 
and  double.  Now  look  closely  at  the  head  of  the  farther  pin.  The 
nearer  one  may  be  seen  doubled,  but  not  sharply.  (2)  Hold  the  tip  of 
a  pencil  in  a  line  with  any  object,  say  a  picture,  on  a  wall  opposite.  In 
looking  at  the  tip  of  the  pencil  the  picture  is  dim.  Now  look  by  the  pen- 
cil at  the  picture,  and  the  point  of  the  pencil  will  be  blurred  and  doubled. 

Accommodation.  —  We  cannot,  at  the  same  time,  see 
distinctly  a  near  and  a  distant  object.  When  we  look  at 


The  Sense  of  Sight. 


219 


a  near  object  the  lens  becomes  thicker,  and  when  we  look 
at  a  distant  object  the  lens  becomes  less  thick.  This  ad- 
justment is  called  accommodation. 


CILIARY  MUSCLE 


FAR  NEAR  CILIARY  PROCESS 

Fig.  98.    Changes  of  the  Lens  in  Accommodation. 

The  Blind  Spot.  —  Light  falling  on  the  optic  nerve  itself  has  no  effect 
in  giving  a  sensation  of  light.  If  the  light  falls  on  the  spot  where  the 
optic  nerve  enters  the  eyeball,  we  see  nothing.  Hence,  this  spot  is 
called  the  blind  spot. 

Experiment  illustrating  the  Blind  Spot.  —  At  the  left  (as  looked  at 
by  the  class)  of  a  long  blackboard  make  a  bright  circular  spot,  three 
inches  in  diameter,  with  white  or  yellow  crayon.  Beginning  at  the 
right  of  this  write  the  figures  i,  2,  3,  etc.,  along  the  whole  length  of  the 
board,  about  eight  inches  apart.  Let  each  pupil  close  the  right  eye  and 
look  at  the  bright  spot.  Then  let  each  read  the  figures,  passing  slowly 
from  one  to  another,  at  the  same  time  noticing  whether  the  bright 
spot  can  be  seen.  To  succeed  in  this  the  eye  must  not  be  allowed  to 
waver.  Have  the  pupils  tell  when  the  bright  spot  disappears,  then 
read  on,  and  note  when  the  spot  reappears. 

Another  Experiment.  —  In  this  experiment  shut  the  right  eye,  and 
be  careful  not  to  let  the  eye  waver. 

>|c  Read  this  line  slowly.  Can  you  see  the  star  all  the  time?  If  the 
star  does  not  disappear  before  reaching  the  end  of  the  line,  let  the  eye 
travel  on  to  the  right  of  the  page,  or  hold  the  book  nearer  the  face. 
In  the  human  eye  the  optic  nerve  enters  the  eye  not  in  the  center,  but 
nearer  the  nose,  so  that  in  turning  the  left  eye  toward  the  right  at  the 
proper  angle,  the  image  of  the  star  falls  upon  the  spot  where  the  optic 
nerve  enters.  As  this  spot  is  insensitive  to  light,  the  star  no  longer 
appears. 


220 


Physiology. 


The  Structure  of  the  Retina.  —  The  retina  is  very  complicated  in  its 
structure.  No  less  than  ten  layers  have  been  distinguished,  as  shown 
in  Fig.  99.  The  rays  of  light  pass  through  the  retina,  and  produce 
their  effect  on  the  rods  and  cones  which  constitute  the  outer  (back) 
layer  ;  and  the  nerve  impulses  aroused  by  the  light  must  return  through 
the  thickness  of  the  retina  to  be  conveyed  along  the  nerve  fibers  of  the 
innermost  layer  of  the  retina  to  the  optic  nerve. 


Inner  or  Vitreous  Surfac 


Path  of 
Inci- 
dent 
Light 


Internal  Limiting  Layer 
Layer  of  Nerve  Fibers 
Layer  of  Nerve  Cells 


Inner  Molecular  Layer 


Inner  Nuclear  Layer 

Outer  Molecular  Layer 

Outer  Nuclear  Layer 

_.  External  Limiting  Layer 

Layer  of  Rods  and  Cones 

Layer  of  Pigment  Cells 

Outer  or  Choroid  Surface 

Fig.  99.    Section  of  the  Retina.    (Waller.) 

Importance  of  the  Retina.  —  The  chief  structure  in  the 
eye  is  the  retina.  Without  this  all  else  is  useless.  If  light 
falls  on  the  retina,  nerve  impulses  pass  along  the  fibers  of 
the  optic  nerve  to  the  brain,  and  we  have  a  sensation  of 
light.  But  in  order  to  see  anything  distinctly,  the  light 
must  fall  on  the  retina  in  such  a  way  as  to  form  a  distinct 
image  of  that  object.  If  the  lens  be  removed,  or  becomes 
opaque,  as  in  "  cataract,"  we  see  objects  very  indistinctly, 
though  we  may  be  able  to  tell  light  from  darkness.  Light 


The  Sense  of  Sight.  221 

from  an  object  passes  through  the  cornea,  aqueous  humor, 
lens,  and  vitreous  humor,  and  the  rays  are  so  refracted  as 
to  form  an  inverted  image  on  the  retina. 

The  Optic  Nerve  not  Sensitive.  —  The  optic  nerve,  while  capable 
of  carrying  nerve  impulses  that  cause  sensations  of  light,  is  not  itself 
sensitive  to  light.  If  the  optic  nerve  be  cut,  it  does  not  give  pain,  but 
gives  the  sensation  of  a  flash  of  light. 

Sympathy  between  the  Two  Eyes.  —  While  most  of  the 
fibers  from  each  optic  nerve  cross  to  the  other  side  of  the 
brain,  some  fibers  go  to  the  same  side  of  the  brain.  We 
can  therefore  better  understand  the  close  sympathy  be- 
tween the  two  eyes. 

Color  Blindness.  —  It  is  found  that  some  persons  cannot  distinguish 
certain  colors.  Blindness  to  red  and  green  are  most  common.  This 
is  a  matter  of  importance  among  railroad  men  and  sailors,  where  it  is 
necessary  to  distinguish  red  and  green  signals. 

Summary.  —  i .  The  eye  is  protected  by  its  bony  surroundings,  lids, 
lashes,  tears,  sensitiveness  of  the  conjunctiva,  etc. 

2.  The  eye  has  three  coats  —  sclerotic,  choroid,  and  retina. 

3.  The  pupil  is  a  hole  in  the  iris,  and  varies  in  size  to  regulate  the 
amount  of  light  admitted. 

4.  The  cornea,  aqueous  humor,  lens,  and  vitreous  humor  form  an 
inverted  image  on  the  retina.     The  eye  is  a  camera,  darkened  inside. 

5.  The  lens  changes  its  thickness  for  seeing  at  different  distances. 

6.  Suitable  glasses  overcome  many  of  the  defects  in  eyesight. 

7.  The  retina  is  an  expansion  of  the  optic  nerve,  and  is  exceedingly 
complicated  in  its  structure. 

8.  The  blind  spot  is  the  place  where  the  optic  nerve  enters  the  eye. 

9.  The  optic  nerve  is  insensitive  to  light,  but  injury  to  it  causes  sen- 
sations of  light. 

10.  Most  of  the  fibers  of  the  optic  nerve  cross  to  the  other  half  of 
the  brain,  but  some  do  not  cross. 

1 1 .  Defects  in  eyesight  are  much  more  common  among  civilized  men 
than  with  the  uncivilized. 


222  Physiology. 

12.   The  care  of  the  eyes  must  be  made  a  subject  of  study  and  care- 
ful thought  by  all  reading  people. 

Questions.  —  i .   What  is  "  cataract "  ? 

2.  What  is  the  cause  of  "  double  vision  "  ? 

3.  Why  does  the  well  eye  sympathize  with  the  affected  one? 

4.  Why  does  looking  at  a  bright  light  often  cause  a  person  to 
sneeze  ? 

5.  What  is  the  condition  of  one  who  is  "cross-eyed"  ? 

6.  Compare  the  pupils  of  a  man,  a  cat,  and  a  cow. 

7.  Does  the  color  of  the  eye  have  any  relation  to  the  strength  of 
eyesight  ? 

8.  Why  is  one  blinded  on  entering  a  bright  room  from  the  dark? 

9.  Why  is  one  going  from  a  bright  room  into  the  dark  unable  to 
see  at  first,  but  gradually  sees  more  distinctly  ? 

10.  Why  can  one  not  see  well  when  the  eye  "waters11  ? 

1 1.  Should  the  lights  which  illumine  a  pulpit  or  platform  be  so  placed 
that  they  can  shine  into  the  eyes  of  the  congregation?     How  should 
they  be  arranged? 

12.  If  each  eye  has  a  blind  spot,  why  are  there  not  blank  spaces  in 
the  field  of  vision  ? 

13.  What  advantage  has  a  stereoscopic  view  over  a  single  view? 
How  are  stereoscopic  views  made  ? 


CHAPTER   XXIV. 
DEFECTS  OF  EYESIGHT  AND  CARE  OF  THE  EYES. 

DEFECTS  OF  EYESIGHT. 

The  Wearing  of  Glasses.  —  It  will  be  noticed  that  many 
people,  even  children,  nowadays  wear  spectacles  or  eye- 
glasses. The  reason  for  this  is  probably  not  entirely 
because  people's  eyes  are  more  defective  now  than  they 
were  fifty  years  ago ;  but  partly  because  everybody,  chil- 
dren and  all,  now  have  to  use  their  eyes  a  great  deal  more 
than  people  did  fifty  years  ago.  Evidence  of  certain  defects 
of  the  eyes  for  which  glasses  are  worn  show  themselves 
more  now  than  they  did  then ;  and  therefore  glasses  have 
to  be  worn  more. 

Symptoms  of  Defective  Eyes,  —  Many  children  suffer 
from  headaches,  or  their  eyes  are  red  and  watery.  Some- 
times they  cannot  plainly  see  the  writing  or  drawing  on 
the  blackboards,  or  they  appear  to  be  stupid,  or  hold  their 
books  close  to  their  eyes  when  reading  or  studying.  Such 
children  probably  have  some  defect  of  the  eyes  which 
glasses  will  remedy.  They  should  be  sent  to  the  oculist 
to  have  their  eyes  examined,  and  if  it  be  found  that  they 
need  glasses,  they  should  wear  them.  It  does  not  always 
follow  that  a  person  does  not  need  glasses  because  he  can 
see  well ;  defects  in  his  eyes  may  require  such  great  effort 
of  the  eye  muscles  that  control  the  focusing  of  the  eyes  as 
to  cause  headaches,  nervousness,  and  other  troubles  which 
a  properly  fitting  pair  of  glasses  will  remedy. 

The  Focus.  —  If  an  object  is  to  be  seen  clearly,  the  eye, 

223 


224  Physiology. 

like  a  photographic  camera,  has  to  be  focused  for  the  par- 
ticular distance  at  which  the  object  is  placed.  In  the 
photographic  camera  the  "  focusing  "  is  done  by  moving 
the  lens  nearer  to  or  farther  from  the  plate  or  film,  accord- 
ing as  the  object  to  be  photographed  is  farther  from  or 
nearer  to  the  camera.  To  get  a  clear  picture  in  pho- 
tography, therefore,  the  length  of  the  camera  must  be 
adjusted  to  the  distance  from  the  camera  of  the  object  to 
be  "taken."  When  the  object  is  a  short  distance  from 
the  camera,  the  "  bellows  "  is  pulled  out  and  the  camera  is 
lengthened;  when  the  object  is  farther  away,  the  "  bellows  " 
is  pushed  in  and  the  camera  is  shortened.  If  the  camera 
is  not  properly  "focused,"  a  clear  photograph  cannot  be 
taken.  So  also  if  one's  eyes  be  not  properly  "  focused,"  he 
cannot  see  clearly. 

The  Crystalline  Lens. — The  eye  is  "focused"  in  a  dif- 
ferent way.  It  cannot  be  made  longer  when  we  look  at 
nearby  things,  or  shortened  when  we  look  at  more  dis- 
tant objects.  Instead  of  this,  the  eye  is  "focused"  by 
changing  the  shape  of  the  "  crystalline  lens,"  which  lies 
just  back  of  the  iris  and  the  pupil,  and  which  performs  in 
the  eye  the  same  service  that  the  glass  lens  does  in  the 
photographic  camera ;  viz.,  it  throws  upon  the  retina,  just 
as  the  camera  lens  does  upon  the  photographic  plate  or 
film,  an  image  of  the  object  at  which  we  are  looking.  Now, 
if  we  could  change  the  thickness  of  the  glass  lens  in  the 
camera,  making  it  thicker  when  photographing  near  objects 
and  thinner  when  photographing  those  farther  away,  we 
should  be  doing  in  the  camera  just  what  is  done  in  the  eye 
when  we  "  focus  "  it.  In  the  eye,  when  we  look  at  a  nearby 
object,  the  crystalline  lens  becomes  thicker ;  when  we  look 
at  a  more  distant  object,  the  crystalline  lens  becomes  thin- 


The  Sense  of  Sight.  225 

ner  or  flatter.  It  is  made  thinner  and  flatter  by  being 
pressed  upon  by  elastic  connective  tissues  between  which 
it  lies,  just  as  a  soft  rubber  ball  will  be  made  flatter  if  it  be 
put  between  two  layers  of  a  handkerchief  and  the  sides  of 
the  handkerchief  pulled  upon. 

The  Natural  Focus. — In  a  state  of  nature  the  eye  is 
used  mostly  for  looking  at  distant  objects,  and  not  for 
looking  at  books  and  near  objects,  as  we  now  have  to  do 
many  hours  at  a  time.  Nature  made  the  eye  so  that  it 
would  be  focused  for  the  distance  by  the  elastic  pull  of  the 
coats  of  the  eyeball.  Elastic  coats  not  being  made  to  work 
by  nervous  energy,  as  muscles  are,  never  grow  tired,  as 
muscles  do  when  they  work.  Nature  made  our  eyes  so 
that  they  would  be  focused  for  distant  objects  without  any 
muscular  action.  Therefore,  our  eyes  do  not  tire  when 
we  look  at  the  distance  ;  they  are  "  resting."  But  in  order 
that  we  may  also  clearly  see  near  objects,  our  eyes  are  so 
made  that  the  crystalline  lens  may  be  made  thicker.  Since 
in  a  state  of  nature  the  eyes  are  not  used  very  often  nor 
for  very  long  periods  in  looking  at  near  objects,  the  focus- 
ing for  near  objects  is  done  by  muscular  action.  Hence, 
the  eyes  become  tired  when  they  are  used  for  long  periods 
in  looking  at  near  objects. 

"  Accommodation. "  —  Everybody  has  seen  a  lady's  arm 
bag  which  closes  by  pulling  the  "  puckering  string."  If 
the  mouth  of  the  bag  were  elastic,  so  that  it  would  open 
itself  if  the  string  were  not  pulled,  and  if  the  string  were 
a  muscle,  it  would  be  something  like  the  arrangement  of 
elastic  coats  and  muscles  by  means  of  which  the  eye  is 
focused.  Just  behind  the  iris,  where  it  is  attached  to  the 
sclerotic  coat  of  the  eyeball,  there  is  a  very  small  circular 
muscle  called  the  "  ciliary  muscle  "  or  "  muscle  of  accom- 


226  Physiology. 

modation."  When  it  contracts,  this  muscle  overcomes  the 
pull  of  the  elastic  tissues,  which  causes  the  flattening  of  the 
crystalline  lens,  which,  being  elastic,  becomes  thicker,  and 
the  eye  is  focused  for  a  near  object. 

Effect  of  Age.  —  As  people  grow  older,  the  crystalline 
lens,  like  the  other  parts  of  the  body,  slowly  loses  its 
elasticity.  Hence  when  the  pressure  is  relaxed  by  the 
action  of  the  muscle  of  accommodation,  the  lens  cannot 
become  thick  enough  to  focus  the  eye  for  very  near 
objects.  For  this  reason  middle-aged  people  cannot  clearly 
see  objects  as  near  to  the  eyes  as  young  people  can.  This 
is  called  "presbyopia,"  from  two  Greek  words  meaning 
"  old-eye." 

In  order  to  see  near  things  clearly,  to  read,  etc.,  middle- 
aged  people  are  compelled  either  to  bold  things  off  at 
arm's  length,  which  is  very  inconvenient,  or  to  put  on 
glasses.  But  through  these  glasses  they  cannot  see  well 
at  the  distance,  because  the  focus  of  the  glasses  is  for  a 
close  object  and  cannot  be  changed. 


(2)   Far-sighted  Eye.  (I)   Normal  Eye.  (3)  Near-sighted  Eye. 

Fig.  100.    Defects  in  Eyesight. 

Far  Sight.  —  It  not  infrequently  happens  that  the  eye- 
ball is  not  long  enough  from  the  front  to  the  back  to 
permit  of  proper  focusing  for  objects  at  a  great  distance 
without  bringing  into  use  the  muscle  of  accommodation. 
In  other  words,  a  perfect  eye  is  focused  for  great  distances 
when  the  muscle  of  accommodation  is  at  rest.  In  the 


The  Sense  of  Sight.  227 

short  eye,  however,  clear  vision  cannot  be  had  at  any  dis- 
tance, unless  the  muscle  of  accommodation  be  actively  at 
work.  Such  eyes  are  called  "  far-sighted,"  or  "  hyper- 
metropic,"  from  three  Greek  words  meaning  "over-meas- 
ured-eye." 

On  account  of  the  fact  that  such  an  eye  cannot  see 
clearly  at  any  distance  without  calling  into  constant  action 
the  muscle  of  accommodation,  that  muscle  has  no  periods 
of  rest  except  during  sleep.  It  is  apt  to  tire  out,  therefore, 
and  the  person  who  has  such  eyes  may  be  subject  to 
headaches  or  other  nervous  troubles.  To  overcome  this 
he  should  wear  glasses.  Although  his  glasses  are  the 
same  kind  that  "  old-sighted "  people  wear,  the  "  far- 
sighted  "  person  can  see  clearly  at  the  distance  as  well 
as  near  by  with  his  glasses,  while  the  "  old-sighted  "  person 
can  see  clearly  only  close  objects  with  his. 

It  not  infrequently  happens  that  the  "  far-sighted  "  per- 
son can  see  equally  well  at  the  distance  with  or  without 
his  glasses.  But  this  is  not  a  sign  that  he  does  not  need 
glasses;  on  the  contrary,  it  is  a  sign  that  he  does  need 
them ;  for  if  he  did  not  need  them,  he  could  not  see  clearly 
with  them. 

If  the  eyes  be  too  long  from  front  to  back,  they  cannot 
see  clearly  at  a  distance,  but  can  see  near  objects  clearly. 
Such  eyes  are  called  "near-sighted,"  or  "myopic,"  from 
two  Greek  words  meaning  "mouse-eye,"  because  near- 
sighted eyes,  like  the  eyes  of  a  mouse,  are  not  infrequently 
quite  prominent. 

The  eyes  of  most  babies  are  "  far-sighted,"  but  as  the 
rest  of  their  bodies  grow,  their  eyes  also  generally  grow 
until  they  become  only  slightly  "far-sighted."  Sometimes 
the  growth  of  the  eyes  does  not  keep  pace  with  the  rest  of 
the  body  and  the  eyes  remain  quite  far-sighted;  in  other 


228  Physiology. 

cases  they  grow  too  rapidly  in  one  direction,  from  the  front 
to  the  back,  and  become  near-sighted.  Children  with  either 
far-sighted  or  near-sighted  eyes  should  wear  glasses,  —  the 
far-sighted  to  avoid  headaches  and  nervous  troubles,  the 
near-sighted  to  enable  them  to  see  plainly  at  a  distance. 

Near  Sight. — When  a  child's  eyes  begin  to  grow  near- 
sighted, there  is  danger  that  the  near-sightedness  will 
increase  if  special  care  is  not  taken  to  prevent  it.  The 
tissues  of  the  child's  eyes  are  comparatively  soft  and  yield- 
ing. Children  nowadays  use  their  eyes  a  great  deal  for 
near  work.  The  nearer  any  object  is  held  to  the  eyes,  the 
more  the  little  muscles  of  accommodation  pull  upon  the  soft 
and  yielding  coats  of  the  eyeball  and  tend  to  stretch  them. 
Not  only  that,  but  the  nearer  any  object  is  held  to  the  eyes, 
the  more  the  eyeballs  turn  inward ;  and  the  more  they  turn 
inward,  the  more  they  are  pressed  upon  and  squeezed  by 
the  six  little  muscles  which  move  each  eyeball.  Thus  pulled 
at  from  within  and  pressed  upon  from  without,  it  not  infre- 
quently happens  that  children's  eyes  become  too  long  from 
before  backward,  that  is,  "  near-sighted." 

Children  can  clearly  see  objects  which  they  hold  very 
near  to  the  eyes,  and  for  this  reason  frequently  get  into  the 
habit  of  doing  so.  This  is  a  very  bad  habit  indeed,  for  it 
tends  to  make  the  eyes  near-sighted,  or,  since  it  tires  the 
muscles  which  turn  the  eyeballs  inward  and  the  muscles  of 
accommodation,  not  infrequently  causes  headaches.  This 
habit  should  be  carefully  and  constantly  corrected,  and  no 
child  should  be  allowed  to  hold  objects  nearer  than  about 
fifteen  inches  from  the  eyes.  If  it  cannot  see  plainly  the 
smallest  print  at  that  distance,  something  is  wrong  with 
the  eyes. 

But  the  necessity  for  the  wearing  of  glasses  is  not  the 


The  Sense  of  Sight.  229 

worst  thing  about  near-sighted  eyes.  The  tendency  of 
near-sighted  eyes  is  to  grow  more  and  more  near-sighted 
unless  great  care  is  taken  to  prevent  it.  Even  that,  how- 
ever, would  not  be  very  bad,  for  it  would  require  only  the 
wearing  of  stronger  and  still  stronger  glasses.  But  as 
the  eyeball  becomes  more  near-sighted,  it  becomes  longer ; 
and  as  it  becomes  longer,  the  membranes  of  which  it  is 
composed,  especially  the  retina  and  the  choroid  coat, 
become  more  and  more  stretched  and  pulled  upon,  until 
they  may  even  become  diseased  or  pull  apart,  so  that 
serious  eye  trouble,  even  blindness,  may  result  from  un- 
cared-for near-sightedness. 

Near-sightedness  may,  therefore,  become  a  disease  of 
the  eyes.  In  fact,  a  near-sighted  eye  may  be  looked  upon 
as  a  diseased  eye.  As  near-sightedness  occurs  practically 
only  among  civilized  people,  it  may  be  called  a  disease  of 
civilization,  and  one  would  naturally  expect  to  find  it  most 
prevalent  among  those  people  who  use  their  eyes  most  for 
near  work.  Such  is  the  fact.  The  Germans,  of  all  people, 
use  their  eyes  most  for  near  work,  and  among  them  near- 
sightedness  is  very  common.  Another  defect  of  the  eyes 
occurs  when  the  clear  front  parts  of  the  eye  (cornea  and 
lens)  are  unequally  curved  so  that  the  rays  of  light  do  not 
converge  properly  in  the  eye,  the  image  on  the  retina  is 
blurred,  and  the  person  thus  afflicted  cannot  see  clearly. 
This  defect  in  vision,  which  is  called  astigmatism,  can  be 
corrected  by  specially  prepared  glasses. 

Importance  of  Proper  Glasses. —  It  will  thus  be  seen  that 
glasses  are  very  frequently  a  necessity  for  children.  Nerv- 
ous, suffering,  peevish,  backward  children,  unable  to  keep 
up  in  their  studies,  are  often  changed  into  sturdy,  happy, 
bright  pupils  who  keep  pace  with  their  classes,  simply  by 


230  Physiology. 

fitting  them  with  proper  glasses.  But  as  the  proper  fitting 
of  glasses  is  not  a  simple  thing,  the  child  should  be  taken 
to  an  oculist,  and  glasses  should  not  be  purchased  of  ped- 
dlers. Ill-fitting  glasses  may  be  worse  than  none  at  all. 

THE   CARE   OF   THE   EYES. 

1.  Objectionable  Light.  —  In  reading  we  wish  light  from 
the  printed  page.     Hence  we  should  avoid  light  entering 
the  eye  from  any  other  source  at  this  time.     While  reading, 
then,  do  not  face  a  window,  another  light,  a  mirror,  or  white 
wall.     White  walls  are  likely  to  injure  the  eyes.     Choose 
a  dark  cover  for  a  reading  table.     Sewing  with  a  white 
apron  on  has  injured  the  eyes.     Direct  sunshine  very  near 
the  book  or  table  is  likely  to  do  harm. 

2.  Position  in  Reference  to  Light.  —  Preferably  have  the 
light  from  behind  and  above.     Sitting  under  and  a  little 
forward  of  a  hanging  lamp  will  allow  the  light  to  fall  on 
the  book  and  keep  it  away  from  the  face.     In  reading  by 
daylight  avoid  cross-lights  so  far  as  possible. 

3.  Electric  Light  —  The  incandescent  electric  light  has 
advantages  in  throwing  the  light  downward  and  in  giving 
out  little  heat ;  but  owing  to  its  irregular  illumination  (due 
to  the  shadow  cast  by  the  wire  or  filament),  it  is  not  well 
suited  for  study  or  other  near  work.     For  this  purpose  an 
Argand  gas  or  kerosene  burner  is  much  to  be  preferred, 
since  it  throws  a  soft,  uniform,  and  agreeable  light  upon 
the  work. 

4.  Reading  Outdoors.  —  Reading  out  of  doors  is  likely  to 
injure  the  eyes,  especially  when  lying   down.     To   read 
while  lying  in  a  hammock  is  bad.     Too  much  light  directly 
enters  the  eye,  and  too  little  falls  upon  the  printed  page. 


The  Sense  of  Sight.  231 

5.  Reading  Heavy  Books.  —  Do  not  hold  the  book  or 
work  nearer  the  eyes  than  is  necessary.     So  far  as  possible 
avoid  continuous  reading  in  large  or  heavy  books  by  arti- 
ficial light.     Such  books  being  hard  to  hold,  the  elbows 
gradually  settle  down  against  the  sides  of  the  body,  and 
thus  the  book  is  held  too  close  to  the  eyes,  or  at  a  bad 
angle,  or  the  body  assumes  a  bad  position. 

6.  Resting    the  Eyes.  —  Frequently  rest  the   eyes    by 
looking  up  and  away  from  the  work,  especially  at  some 
distant  object.     One  may  rest  the  eyes  while  thinking  over 
each  page  or  paragraph,  and  thus  really  gain  time  instead 
of  losing  it. 

7.  Strength  of  Light.  —  Have  light  that  is  strong  enough. 
At  twice  the  distance  from  a  lamp  the  light  is  only  one 
fourth  as  strong.     Reading  just  before  sunset  is  not  wise. 
One  is  often  tempted  to  go  on,  not  noticing  the  gradual 
fading  of  the  light. 

8.  Evening  Reading.  —  Do  the  most  difficult  reading  by 
daylight,  and  save  the  better  print  and  the  books  that  are 
easier  to  hold  for  work  by  artificial  light.     Writing  is  usu- 
ally much  more  trying  to  the  eyes  than  reading.     By  care- 
fully  planning   his   work   one   may   economize   eyesight. 
Weak  eyes,  by  proper  care,  may  outlast  and  do  more  work 
than  those  naturally  stronger,  but  injured  by  abuse.    Read- 
ing before  breakfast  by  artificial  light  is  usually  bad. 

9.  Reading   during    Convalescence.  —  Many    eyes    are 
ruined  during  convalescence.     At  this  time  the  whole  sys- 
tem  is   weak  —  including   the   eyes.     There   is  a   strong 
temptation  to  read,  perhaps  to  while  away  the  time,  per- 
haps to  make  up  for  lost  time  in  school  work.     This  is  a 
time  when  a  friend  may  show  his  friendship. 


232  Physiology. 

10.  Irritation  of  the  Eyes.  —  If  one  finds  himself  rubbing 
his  eyes,  it  is  a  sign  that  they  are  irritated.     Stop  read- 
ing, find  the  cause,  and  do  not  read  on  unless  the  irritation 
ceases.     If  any  foreign  object,  as  a  cinder,  lodges  in  the 
eye,  it  is  better  not  to  rub  the  eye,  but  to  draw  the  lid 
away  from  the  eyeball  and  wink  repeatedly ;  the  increased 
flow  of  tears  may  dissolve  and  wash  the  matter  out.     If  it 
be  a  sharp-cornered  cinder,  rubbing  may  merely  serve  to 
fix  it  more  firmly  in  the  conjunctiva.     If  it  does  not  soon 
come  out,  the  lid  may  be  rolled  up  over  a  pencil,  taking 
hold  of  the  lashes  or  the  edge  of  the  lid.     The  point  of  a 
blunt  lead  pencil  is  a  convenient  and  safe  instrument  with 
which  to  remove  the  particle. 

11.  Keep  the  Eyes  Clean.  —  Be  careful  to  keep  the  eyes 
clean.     Do  not  rub  the  eyes  with  the  fingers.     Aside  from 
consideration  of  rules  of  etiquette,  there  is  danger  of  intro- 
ducing foreign  matter  that  may  be  very  harmful.     It  is 
very  desirable  that  each  person  have  his  individual  face 
towel.       By   not   observing   this    rule   certain   contagious 
diseases  of  the  eyes  often  spread  rapidly. 


CHAPTER   XXV. 
TASTE,  SMELL,  HEARING,  AND  THE  VOICE. 

Uses  of  the  Sense  of  Taste.  —  The  sense  of  taste  helps 
us  in  judging  of  the  fitness  of  food.  By  reflex  action  the 
taste  of  agreeable  substances  aids  in  digestion  by  stimulat- 
ing the  glands,  especially  the  salivary  glands. 

The  Papillas.  —  The  surface  of  the  tongue  is  covered 
with  papillas.  Most  of  them  are  slender,  and  like  the 

Papillas 


Glosso-pharyngeal 
Nerve  (9th) 


Gustatory  Branch  of  Fifth  Nerve 
Fig.  101.     Nerves  and  Papillas  of  the  Tongue. 

papillas  of  the  skin,  are  organs  of  touch.  Scattered  among 
these  are  larger  papillas  in  which  are  the  endings  of  the 
nerves  of  taste. 

The  Nerve  Supply  of  the  Tongue.  —  The  nerves  of  taste 
are  the  glosso-pharyngeal,  distributed  to  the  back  part  of 
the  tongue,  and  the  gustatory  in  the  front  part.  The  tip 
of  the  tongue  seems  to  be  most  sensitive  to  sweets  and 
salts,  the  back  part  to  bitters,  and  the  sides  to  acids. 
1 6— PHY  233 


234 


Physiology. 


Solution  Necessary  for  Tasting  — Substances  must  be 
dissolved  before  they  can  be  tasted.  If  the  tongue  be 
wiped  dry,  and  a  few  grains  of  salt  or  sugar  be  placed  on 
it,  the  taste  will  not  be  perceived  for  a  little  time.  Insol- 
uble substances  give  no  taste. 

Flavors.  —  What  we  call  flavors  affect  us  more  through  the  sense  of 
smell  than  through  taste.  If  the  nose  be  held  shut,  a  piece  of  onion 
placed  on  the  tongue  does  not  produce  what  we  usually  call  the  taste 
of  the  onion.  By  holding  the  nose  we  may  get  rid  of  the  disagreeable 
part  of  taking  certain  medicines.  Let  the  pupil  experiment  with  various 
substances  as  above  indicated. 

The  Sense  of  Smell.  —  The  nerves  of  smell,  the  olfactory 
nerves,  are  distributed  in  the  walls  of  the  nasal  passages. 
The    sense   of 
odor   gives   us 
information  as 
to    the   quality 
of     food     and 
drink,  and  more 
especially  as  to 
the   quality  of 
the  air  we  breathe.   Hence 
we  find  the  organ   placed 
at     the    opening    of     the 
respiratory    passages,   and 
close     to    the     organ     of 
taste. 


Olfactory  Bulb 


Olfactory  Nerves. 

Branches  of 
Fifth  Nerve 


Turbinated  Bones 


102. 


Nerves  of  the  Outer  Wall  of  the 
Nasa>   Cavity. 


Why  we  Sniff.  — In  quiet  breathing  the  air  passes  along  the  lower 
air  passages  just  above  the  hard  palate.  When  we  wish  to  test  the 
quality  of  the  air,  we  sniff,  that  is,  make  a  sudden  inspiration  by  jerking 
the  diaphragm  down,  and  air  from  the  outside  then  rushes  into  the 
upper  nasal  passages,  over  the  walls  of  which  the  olfactory  nerves  are 
spread  in  the  mucous  membrane.  In  inflammation,  as  from  a  cold, 
the  narrow  nasal  passages,  especially  the  upper,  are  often  closed. 


Taste,  Smell,  Hearing,  and  the  Voice.      235 

The  Parts  of  the  Ear.  —  The  parts  of  the  ear  are  the 

external,  the  middle,  and  the  internal  ear. 

The  External  Ear.  —  The  external  ear  gathers  the  sound 
waves,  and  directs  them  into  the  opening  of  the  ear,  but 
the  loss  of  the  external  ear  does  not  seriously  interfere 
with  hearing.  The  passage  leading  inward  from  the  ear 
extends  about  an  inch,  and  is  then  completely  shut  off 


Semicircular  Canals    "** 


Stirrup 


Fig.  103.    Structure  of  the  Ear. 

from  the  cavities  beyond  by  a  thin  membranous  partition, 
the  tympanic  membrane  or  drum  skin.  This  passageway 
is  guarded  by  hairs,  and  is  further  protected  by  wax 
secreted  by  glands  of  the  lining. 

The  Middle  Ear.  —  Beyond  the  membrane  of  the  tym- 
panum is  a  cavity  called  the  middle  ear.  Extending  across 
the  cavity  of  the  middle  ear  is  a  chain  of  very  small  bones, 
the  hammer,  anvil,  and  stirrup,  the  hammer  being  attached 
to  the  inner  surface  of  the  membrane  of  the  tympanum, 


236  Physiology. 

and  the  stirrup  being  fastened  by  its  base  to  the  wall  of 
the  internal  ear. 

The  Eustachian  Tube.  —  The  middle  ear  communicates 
with  the  pharynx  by  means  of  a  narrow  tube  called  the 
eustachian  tube.  It  admits  air  to  equalize  the  pressure  on 
the  two  sides  of  the  tympanic  membrane.  This  tube  is 
closed  most  of  the  time,  but  opens  when  we  swallow. 

The  Internal  Ear.  —  The  internal  ear  consists  of  several 
complicated  cavities  and  tubes  which  contain  a  liquid  in 
which  rest  the  nerves.  The  principal  cavity  is  the  cochlea, 
or  snail-shell  cavity,  in  which  the  nerve  endings  are  con- 
nected with  an  exceedingly  complicated  apparatus. 

The  Production  of  Sound.  —  Sound  waves  set  the  drum 
skin  or  membrane  of  the  tympanum  in  vibration;  the 
vibrations  are  conveyed  by  the  chain  of  bones  across  the 
middle  ear  to  the  liquid  of  the  inner  ear.  Through  the 
complicated  apparatus  of  the  snail  shell  the  vibrations  of 
the  liquid  are  made  to  start  nerve  impulses  in  the  fibers  of 
the  auditory  nerve,  and  when  these  nerve  impulses  are 
rightly  received  and  interpreted  by  the  brain,  we  have  a 
sensation  called  sound. 

The  Equilibrium  Sense.  —  Probably  most  of  the  senses  contribute 
to  the  maintaining  of  the  equilibrium  of  the  body  by  giving  information 
as  to  position,  motion,  etc.,  especially  sight  and  the  muscular  sense. 

Only  that  part  of  the  auditory  nerve  which  is  distributed  in  the  "  snail 
shell "  of  the  ear  is  now  supposed  to  have  to  do  with  hearing.  There 
seems  to  be  good  evidence  that  the  semicircular  canals  inform  us  as 
to  changes  of  the  position  of  the  body,  and  they  are  regarded  as  the 
seat  of  an  "  equilibrium  sense." 

The  Care  of  the  Ear.  —  In  cleaning  the  ear  no  hard  sub- 
stance should  be  used  ;  even  the  finger  nail  is  likely  to 
do  harm.  A  moistened  cloth  should  be  used.  It  is  not 


Taste,  Smell,  Hearing,  and  the  Voice.      237 


well  to  stuff  the  ears  with  cotton.  If  there  is  any  trouble 
with  the  hearing,  of  course  a  physician  should  be  consulted 
without  delay. 

Colds  and  Deafness.  —  A  cold  often  produces  inflamma- 
tion of  the  mucous  membrane  of  the  pharynx.  This  in- 
flammation may  extend  along  the  eustachian  tube  to  the 
middle  ear  and  affect  the  hearing.  See  "Adenoids,"  p.  95. 


Epiglottis 
Base  of  Tongue 

Hyoid  Bone 

False  Vocal  Cord 
Ventricle 
Vocal  Cord 


Cartilage 


Trachea 

FROM    RIGHT  TO   LEFT  MEDIAN 

Fig.    104.    Longitudinal  Sections  of  the  Larynx. 

The  Ear  and  the  Voice.  —  The  delicate  structure  of  the 
ear  is  fully  matched  by  the  fine  adjustment  and  range  of 
the  voice.  The  voice  is  produced  in  the  larynx  at  the  upper 
end  of  the  windpipe.  The  projecting  angle  of  the  larynx 
is  called  "  Adam's  apple." 

The  Vocal  Cords.  —  The  vocal  cords  are  not  cord-like. 
They  are  mere  ridges  projecting  inward  from  the  sides  of 
the  larynx.  They  maybe  stretched  to  various  degrees  and 
placed  in  different  positions,  according  to  the  sound  that 
is  to  be  produced. 


238  Physiology. 

The  Position  of  the  Vocal  Cords.  —  While  we  are  quietly 
breathing,  the  vocal  cords  lie  back,  like  low  ridges,  against 
the  sides  of  the  larynx,  and  offer  nearly  the  whole  channel 
of  the  larynx  for  the  free  passage  of  air  for  breathing  pur- 
poses. But  when  we  wish  to  produce  vocal  sound,  the 
vocal  cords  are  made  to  stand  out  farther  from  the  side 
walls,  and  interfere  with  the  free  passage  of  the  air.  The 
vocal  cords  are  attached  close  to  each  other  in  front,  but 
at  the  back  of  the  larynx  they  diverge  widely,  forming  a 


Epiglottis 
False  Vocal  Cords  — 

True  Vocal  Cords  . — 


i 
Glottis  Narrowed,  High  Note  Glottis  Wider,  Quiet  Breathing 

Fig.  105.    The  Vocal  Cords,  seen  from  Above 

letter  V,  with  the  angle  of  the  V  just  back  of  Adam's 
apple.  "When  changes  in  the  voice  or  in  breathing  are 
being  made,  the  white  glistening  vocal  cords  may  be  seen 
to  come  together  or  to  go  apart  like  the  blades  of  a  pair  of 
scissors."  In  a  high  note  the  cords  are  close  together  and 
nearly  parallel.  As  the  air  is  forced  past  the  edges  of  the 
vocal  cords,  they  are  set  in  vibration,  and  produce  the 
sound  called  the  voice. 

Illustration  of  the  Vocal  Cords.  —  The  principle  of  the  action  of  the 
vocal  cords  can  be  illustrated  by  the  common  toy  known  as  the  squeak- 
ing balloon,  or  "squawker."  Here  the  air  is  driven  out  past  a  band  of 
rubber  stretched  across  the  inner  end  of  the  tube.  If  instead  of  one 
band  with  both  edges  free,  we  were  to  tie  on  the  inner  end  of  the  tube 
two  bands  of  rubber,  each  covering  the  outer  edge  of  the  tube,  leaving 
the  inner  edge  of  the  rubber  free,  and  with  the  two  bands  touching  at 
one  end  and  considerably  separated  at  the  other  end,  we  would  have  a 
pretty  fair  resemblance  to  the  larynx. 


Taste,  Smell,  Hearing,  and  the  Voice.      239 

Loudness  of  Voice.  —  The  loudness  of  the  voice  depends  on  the  force 
with  which  the  air  is  driven  past  the  cords,  and  on  the  size  and  con- 
dition of  the  cords  themselves. 

Pitch  of  Voice.  —  Pitch  depends  on  the  rapidity  of  the  vibrations, 
which  is  determined  by  the  length  of  the  cords  and  their  tension. 
Other  things  being  equal,  the  size  of  the  larynx  would  determine  the  pitch. 

Voice  and  Speech.  —  The  larynx  by  itself  produces  vocal  sound 
merely.  In  speech  the  sounds  produced  in  the  larynx  are  much  modi- 
fied by  the  lips,  tongue,  teeth,  cheeks,  etc.  We  have  voice  as  soon  as 
born,  but  we  only  gradually  acquire  the  power  of  speech.  This  dis- 
tinguishes man  from  the  animals  below  him. 

Summary.  —  i.  Taste  enables  us  to  judge  of  the  quality  of  food,  and 
it  indirectly  influences  digestion. 

2.  The  tongue  has  two  nerves  of  taste,  the  fifth  pair  of  cranial  nerves 
supplying  the  front,  and  the  ninth  pair  the  base. 

3.  So-called  flavors  affect  the  sense  of  smell  more  than  that  of  taste. 

4.  The  sense  of  smell  tests  food  and  air. 

5.  Agreeable  odors  promote  respiration. 

6.  The  ear  consists  of  the  outer,  middle,  and  inner  ear.     In  the 
inner  ear  are  the  endings  of  the  auditory  nerve. 

7.  The  semicircular  canals  have  to  do  with  the  sense  of  equilibrium 
and  not  with  hearing. 

8.  Colds  and  catarrh  often  seriously  affect  hearing. 

9.  The  larynx  is  very  complicated.     Various  muscles  moVe  the  car- 
tilages and  vary  the  length   and  tension  of  the  vocal  cords,  and  thus 
produce  the  varying  degrees  of  pitch. 

10.  The  vocal  cords  are  not  cords,  but  are  band-like  ridges  on  the 
sides  of  the  larynx. 

11.  The  higher  animals  have  voice  but  not  speech. 

12.  Whispering  is  speech  without  voice. 

13.  The  larynx  is  affected  by  "  colds  "  and  catarrh. 

Questions.  —  i .    How  may  the  sense  of  taste  be  blunted  ? 

2.  What  is  the  effect  of  inhaling  menthol  ? 

3.  Does  a  person  who  is  deaf  in  one  ear  hear  "  half  as  well "  as  before  ? 

4.  Which  of  the  senses  goes  to  sleep  first  when  we  go  to  bed  ? 

5.  In  what  order  do  the  other  senses  go  to  sleep  ? 

6.  In  what  order  do  the  senses  waken  in  the  morning  ? 

7.  Why  does  one  become  hoarse  from  hearing  others  shouting  ? 


CHAPTER   XXVI. 
ACCIDENTS.— WHAT   TO   DO    TILL   THE    DOCTOR    COMES. 

How  to  Stop  Flow  of  Blood  from  Arteries.  —  In  case  of  bleeding 
from  an  artery  the  blood  comes  in  jets.  Pressure  should  be  applied 
between  the  cut  and  the  heart.  To  know  where  to  apply  the  pressure, 
study  the  course  of  the  main  arteries.  By  examining  Fig.  32  it  will  be 
seen  that  the  arteries  to  the  arms  pass  down  the  inside  of  the  upper 
arm.  Here  they  come  near  the  surface.  By  putting  a  thick  book  or 
roll  under  the  armpit  and  pressing  the  arm  down  firmly,  the  artery  may 
be  compressed. 

Bleeding  from  the  Upper  Arm.  —  In  case  of  a  deep  cut  in  the  lower 
part  of  the  arm,  a  handkerchief  should  have  a  knot  tied  in  it,  and  the 
knot  placed  over  the  artery ;  that  is,  on  the  inside  of  the  arm  just  below 
the  armpit.  Pass  the  handkerchief  around  the  arm  and  tie  it  loosely. 
Then  run  a  stick  through  it,  and  twist  till  the  knot  is  drawn  tightly 
against  the  artery.  Instead  of  a  knot,  a  potato,  or  anything  else  to 
make  a  firm  lump,  may  be  used.  (See  Fig.  32.) 

Bleeding  from  the  Neck.  —  In  studying  the  pulse,  we  found  the 
carotid  artery  in  the  neck.  If  a  deep  cut  has  been  made  in  the  upper 
part  of  the  neck,  it  may  be  possible  to  stop  the  flow  by  compressing 
the  artery  lower  down  the  neck. 

Wounds  in  the  Thigh.  —  The  femoral  artery  comes  near  the  surface 
in  the  groin.  Pressure  may  be  applied  here  in  the  same  way  to  stop 
bleeding  from  a  cut  farther  down  the  thigh.  In  the  angle  back  of  the 
knee,  pressure  may  compress  the  artery  supplying  the  leg.  In  case  of 
severe  wounds,  pressure  should  be  applied  immediately  to  the  wound. 
Sometimes  it  is  well  to  make  a  plug  of  cloth  and  press  upon  the  cut. 

Bleeding  from  Veins.  —  In  case  of  bleeding  from  veins,  holding  the 
part  up  may  check  the  flow.  If  necessary  to  apply  pressure,  it  should 
be  beyond  the  cut,  instead  of  between  it  and  the  heart,  as  in  the  case  of 
the  artery. 

240 


Accidents.  241 

Hemorrhage  of  the  Lungs  or  Stomach.  —  Blood  from  the  lungs  is 
bright,  frothy,  and  salty ;  from  the  stomach  is  usually  dark  and  sour. 
In  case  of  bleeding  from  the  lungs  or  stomach,  let  the  person  rest 
quietly  on  a  lounge  or  easy-chair.  Give  him  some  bits  of  ice  to  swallow, 
and  call  a  physician. 

Bleeding  from  the  Nose.  —  Nosebleed  may  sometimes  be  stopped  by 
pressing  firmly  at  the  base  of  the  nose.  Do  not  lean  forward,  as  this  posi- 
tion aids  the  flow.  Sit  up,  and  hold  up  the  head,  and  hold  a  cloth  under 
the  nose.  Apply  cold  water  or  ice  to  the  nose  and  to  the  back  of  the 
neck.  If  this  does  not  stop  it,  inject  cold  water,  with  a  little  salt  or 
soda  in  it,  into  the  nose.  Often  the  flow  may  be  stopped  by  pressing 
firmly  on  the  upper  lip  at  the  sides  of  the  nose.  If  these  attempts  fail, 
a  long  strip  of  cloth  may  be  used  to  plug  the  nostril,  pushing  the  cloth 
in  a  little  at  a  time,  and  leaving  the 'ends  so  it  can  be  pulled  out.  This 
should  not  be  removed  till  a  long  time  after  the  flow  is  checked,  as  it 
may  start  the  bleeding  afresh.  After  an  attack  of  this  kind  avoid  blow- 
ing the  nose,  as  this  often  starts  bleeding  again. 

Treatment  of  Burns.  —  Plunge  the  burned  part  into  cold  water.  As 
soon  as  possible  apply  a  solution  of  cooking  soda  (a  tablespoonful  of 
bicarbonate  of  soda  to  a  teacup  of  water)  ;  or  lay  a  wet  cloth  on  the 
burned  part  and  put  the  soda  on  the  cloth.  Afterwards  apply  vaseline, 
and  renew  the  vaseline  till  the  wound  is  healed.  A  mixture  of  equal  parts 
of  sweet  oil  and  limewater  makes  a  good  liniment  for  dressing  burns. 

Danger  from  Burning  Clothing.  —  If  the  clothing  takes  fire,  there 
is  added  to  the  danger  of  burning  the  body,  the  further  risk  of  inhaling 
the  flame  and  heated  air.  It  is  best  to  lie  down  and  roll  or  wrap  the 
body  in  any  cloths  at  hand,  —  rugs,  shawls,  etc.  Running  serves  to  fan 
the  flames.  Hence,  if  a  person  whose  clothing  is  on  fire  has  lost 
presence  of  mind  and  starts  to  run,  throw  him  to  the  ground,  putting  a 
wrap  of  some  kind  around  the  body  at  the  same  time  if  possible.  Roll- 
ing on  the  ground  or  floor  in  itself  would  very  likely  put  out  a  small 
flame. 

Treatment  of  Fainting.  —  Lay  the  body  flat  on  the  back.  Keep  the 
crowd  away,  and  give  plenty  of  fresh  air.  Loosen  the  clothing  about  the 
neck  and  waist.  Sprinkle  cold  water  on  the  face,  but  do  not  drench 
the  body  with  a  quantity  of  water.  Apply  smelling  salts  (ammonia)  to 
the  nostrils  ;  nib  the  limbs  toward  the  body.  If  these  remedies  do  not 
soon  restore  consciousness,  send  for  a  physician.  A  faint  is  not  usually 


242  Physiology. 

a  serious  matter.     Bad  ventilation,  disagreeable  odors,  or  even  the  over- 
sweet  odors  of  such  flowers  as  the  tuberose,  may  cause  fainting. 

Broken  Bones.  —  Keep  the  patient  as  quiet  as  possible  till  the  physi- 
cian arrives.  If  there  is  inflammation,  cold  water  may  be  applied. 
Cooling  applications  are  desirable  in  case  of  severe  bruises.  If  it  is 
necessary  to  carry  the  patient,  lay  him  on  a  board,  or  at  least  keep  the 
injured  part  as  quiet  as  possible ;  a  cane  or  umbrella  may  be  tied  along- 
side a  leg,  and  supported  by  a  pillow  or  a  coat.  Otherwise  the  sharp 
ends  of  the  bones  may  cut  the  flesh  or  even  blood-tubes. 

Sunstroke.  —  Lay  the  patient  in  the  shade  and  pour  cold  water  over 
the  head. 


Fig.  106.    Resuscitation  from  Drowning.    (Lincoln,  3  Figures.) 

(Position   I.) 

TREATMENT   OF   THE   DROWNED. 

(As  given  by  the  Michigan  Board  of  Health.} 

RULE  I .  Remove  all  obstructions  to  breathing.  Instantly  loosen  or 
cut  apart  all  neck  and  waist  bands ;  turn  the  patient  on  his  face,  with 
the  head  down  hill ;  stand  astride  the  hips  with  your  face  toward  his 
head,  and,  locking  your  fingers  together  under  his  belly,  raise  the  body 
as  high  as  you  can  without  lifting  the  forehead  off  the  ground  (Fig. 
106,  Position  i),  and  give  the  body  a  smart  jerk  to  remove  mucus  from 


Accidents. 


243 


the  throat  and  water  from  the  windpipe ;  hold  the  body  suspended  long 
enough  to  count  slowly,  one,  two,  three,  four,  five,  repeating  the  jerk 
more  gently  two  or  three  times. 

RULE  2.  Place  the  patient  on  the  ground  face  downward,  and,  main- 
taining all  the  while  your  position  astride  the  body,  grasp  the  points  of 
the  shoulders  by  the  clothing,  or,  if  the  body  is  naked,  thrust  your  fingers 
into  the  armpits,  clasping  your  thumbs  over  the  points  of  the  shoulders, 
and  raise  the  chest  as  high  as  you  can  (Fig.  107,  Position  2)  without 
lifting  the  head  quite  off  the  ground,  and  hold  it  long  enough  to  count 


Fig.  107.    Resuscitation  from  Drowning. 
(Position  2.) 

slowly  one,  two,  three.  Replace  him  on  the  ground,  with  his  forehead 
on  his  flexed  arm,  the  neck  straightened  out,  and  the  mouth  and  nose 
free.  Place  your  elbows  against  your  knees,  and  your  hands  upon  the 
sides  of  his  chest  (Fig.  108,  Position  3),  over  the  lower  ribs,  and  press 
downward  and  inward  with  increasing  force  long  enough  to  count 
slowly  one,  two.  Then  suddenly  let  go,  grasp  the  shoulders  as  before, 
and  raise  the  chest  (Position  2),  then  oress  upon  the  ribs,  etc.  (Position 
3).  These  alternate  movements  should  be  repeated  ten  or  fifteen  times 
a  minute  for  an  hour  at  least,  unless  breathing  is  restored  sooner.  Use 
the  same  regularity  as  in  natural  breathing. 


244 


Physiology. 


RULE  3.  After  breathing  has  commenced,  restore  the  animal  heat. 
Wrap  him  in  warm  blankets,  apply  bottles  of  hot  water,  hot  bricks,  or 
anything  to  restore  heat.  Warm  the  head  nearly  as  fast  as  the  body 
lest  convulsions  come  on.  Rubbing  the  body  with  warm  cloths  or  the 
hand,  and  slapping  the  fleshy  parts,  may  assist  to  restore  warmth,  and 
also  the  breathing.  If  the  patient  can  surely  swallow,  give  hot  coffee, 
tea,  milk.  Alcoholic  liquors  are  liable  to  produce  depression.  Place 


Fig.  108. 


Resuscitation  from  Drowning. 
(Position  3.) 


the  patient  in  a  warm  bed,  and  give  him  plenty  of  fresh  air ;  keep  him 
quiet. 

Avoid  Delay !  —  A  moment  may  turn  the  scale  for  life  or  death.  Dry 
ground,  shelter,  warmth,  stimulants,  etc.,  at  this  moment  are  nothing  — 
artificial  breathing  is  everything  —  is  the  one  remedy  —  all  others  are 
secondary.  Do  not  stop  to  remove  wet  clothing.  Precious  time  is 
wasted,  and  the  patient  may  be  fatally  chilled  by  the  exposure. 

First  restore  Breathing.  —  Give  all  your  attention  and  effort  to  re- 
store breathing  by  forcing  air  into,  and  out  of,  the  lungs.  If  the  breath- 
ing has  just  ceased,  a  smart  slap  on  the  face  or  a  vigorous  twist  of  the 
hair  will  sometimes  start  it  again,  and  may  be  tried  incidentally. 


Accidents.  245 

Before  natural  breathing  is  fully  restored,  do  not  let  the  patient  lie  on 
his  back  unless  some  person  holds  his  tongue  forward.  The  tongue  by 
falling  backward  may  close  the  windpipe  and  cause  fatal  choking. 

Prevent  friends  from  crowding  around  the  patient  and  excluding  the 
fresh  air ;  also  from  trying  to  give  stimulants  before  the  patient  can 
swallow.  The  first  causes  suffocation ;  the  second,  fatal  choking. 

Do  not  give  up  too  soon  :  you  are  working  for  life.  Any  time  within 
two  hours  you  may  be  on  the  very  threshold  of  success  without  there 
being  any  sign  of  it. 

Learn  to  Swim.  —  Of  course,  persons  who  cannot  swim  ought  not  to 
go  out  in  a  boat  without  taking  along  some  sort  of  a  float  that  may 
serve  as  a  life-preserver.  Some  of  the  rubber  cushions  serve  well  for 
this.  Every  father  neglects  his  duty  if  he  does  not  teach  his  children, 
girls  as  well  as  boys,  to  swim  and  to  float.  One  cool,  trained  person 
may  save  the  lives  of  a  whole  boat  load. 

When  a  Boat  Upsets.  —  In  case  an  ordinary  rowboat  is  overturned, 
one  should  not  attempt  to  climb  into  it  or  upon  it.  It  takes  very  little 
to  float  a  person  in  water,  as  the  body  is  only  a  little  heavier  than 
water ;  in  fact,  if  a  person  fills  the  lungs  and  lies  back  in  the  water  his 
face  and  nose  will  keep  above  water,  and  a  person  (at  any  rate  without 
clothing)  can  float  in  this  way  for  some  time  if  he  breathes  lightly. 
Few  persons  have  been  taught  these  facts,  and  most  of  those  who  have 
learned  them  lose  their  presence  of  mind,  and  waste  their  breath  and 
strength  in  wild  and  fruitless  splashing.  If  a  boat  be  overturned,  those 
who  can  swim  should  help  those  who  cannot  to  get  hold  of  the  edge 
of  the  boat,  but  not  permit  them  to  climb  upon  it.  A  small  plank 
will  float  a  person  if  he  does  not  try  to  lift  much  of  his  body  out  of 
the  water. 

Suffocation  in  Wells.  —  Persons  are  sometimes  suffocated  by  carbon 
dioxid  in  wells  and  cisterns.  Before  going  down  into  a  well,  it  is  a 
safe  precaution  to  lower  a  lighted  candle.  If  this  is  extinguished,  a 
warning  is  given.  If  a  second  person  goes  down  after  one  who  has 
become  unconscious,  great  care  must  be  taken  that  two  lives  are  not 
lost.  A  rope  should  be  firmly  tied  about  the  body,  a  hook,  attached  to 
another  rope,  taken  to  catch  into  the  clothing  of  the  first,  and  the 
rescuer  should  be  lowered  quickly  and  brought  up  immediately.  A 
small  rope  or  large  cord  might  be  carried,  by  pulling  which  the  signal 
is  given  to  pull  up.  In  resuscitating  from  carbon  dioxid  suffocation  use 


246  Physiology. 

the  same  method  as  after  drowning,  except  the  first  part,  which  is  to 
remove  water  from  the  windpipe,  etc. 

Poisons  and  their  Antidotes.  —  Several  of  the  common  drugs  and 
remedies  kept  about  the  house  are  more  or  less  poisonous.  The  proper 
antidote  for  each  should  be  known  and  kept  at  hand.  In  the  first  place, 
all  such  materials  should  be  kept  locked  up  so  they  will  not  be  taken 
by  children,  or  by  mistake,  as  in  the  haste  of  getting  medicine  in  the 
night.  Again,  all  grown  persons  in  the  family  should  be  instructed  as 
to  the  effects  of  each  poison,  and  taught  its  antidote.  As  soon  as  any 
new  poisonous  drug  is  bought,  it  should  be  made  a  point  to  read  up 
about  it,  and  procure  an  antidote.  Every  one  should  know  that 
strychnin  causes  spasms,  that  opium  brings  on  stupor,  with  contracted 
pupils,  etc. 

Objects  of  Treatment.  —  Treatment  aims  at  three  things,  (i)  to  get 
rid  of  the  poison,  (2)  to  neutralize  what  remains  and  prevent  further 
action,  (3)  to  remedy  the  effects  already  produced. 

1.  Mtfstard  a  Common  Emetic.  —  The  most  common  emetic  is  mus- 
tard ;  a  tablespoonful  in  a  cup  of  warm  water ;  give  half  of  it,  following 
with  free  drinking  of  warm  water,  then  give  the  rest  of  the  mustard. 
Do  not  wait  for  it  to  dissolve,  but  stir  quickly  and  give  at  once.     Pro- 
voke vomiting  by  tickling  the  throat  with  a  feather  or  with  the  finger. 
If  the  mouth  of  the  patient  cannot  readily  be  opened,  insert  the  thumbs 
inside  the  cheeks  and  back  of  the  teeth.     If  mustard  is  not  at  hand,  a 
strong  solution  of  table  salt  will  serve.     In  a  few  cases,  such  as  poison- 
ing by  ammonia,  lye,  etc.,  it  is  considered  best  not  to  administer  an 
emetic,  but  to  try  to  neutralize  the  effect. 

2.  Neutralize  the  Poison.  —  To  neutralize  a  poison  this  general  rule 
should  be  known  :  an  alkali  may  be  neutralized  by  an  acid,  and  vice  versa. 
For  example,  lye  with  vinegar,  carbolic  acid  with  alcohol  and  whiting 
or  magnesia,  etc.     Some  acids  and  alkalis  are  always  about  a  house. 

3.  Give  Something  Soothing.  —  After  any  irritant  poison  some  mild 
and  soothing  substance  should  be  given,  —  white-of-egg,  milk,  mucilage 
and  water,  flour  and  water,  gruel,  olive-  or  castor-oil.     These  materials 
are  partly  for  neutralizing  the  poison,  and  are  also  soothing  in  their 
effect.     If  a  patient  is  drowsy,  some  stimulant  may  be  given,  as  strong 
coffee  (after  opium) .     Of  course  a  physician  should  be  sent  for  imme- 
diately, as  the  after-treatment  is  of  great  importance. 


Accidents.  247 

Wounds  from  Thorns  and  Rusty  Nails.  —  Promote  bleeding  by  rub- 
bing and  pressing  the  wound  and  bathing  with  warm  water.  Or  suck 
the  wound.  This  tends  to  remove  any  injurious  matter.  Apply 
poultices. 

Bites  of  Cats,  Dogs,  etc.  —  If  the  animal  is  rabid  (mad),  suck  the 
wound  and  cauterize  quickly.  A  poker  or  nail  heated  red  hot  is  best 
for  cauterizing.  If  one  cannot  do  this  promptly,  get  lunar  caustic  with 
which  to  cauterize ;  strong  acid  or  alkali,  or  a  coal  of  fire,  may  be  ap- 
plied at  once  to  the  wound ;  the  coal  on  a  cigar  may  be  used.  Do  not 
kill  the  animal  if  there  is  doubt.  Keep  it  confined,  and  if  it  proves  a 
false  alarm  much  anxiety  will  be  saved. 

Snake  Bites.  —  Apply  ligatures  around  the  part  between  it  and  the 
heart.  Suck  the  wound  (there  is  no  danger  in  this  if  there  are  no  sores 
or  cracks  in  the  skin  of  the  mouth ;  venom  is  not  a  stomach  poison). 
Then  apply  caustics,  or  a  live  coal.  Wash  the  wound  with  vinegar  or 
strong  salt  solution.  If  ammonia  water  is  at  hand,  add  five  teaspoon- 
fuls  to  a  pint  of  water  and  drink  this.  Ammonium  carbonate,  ten  per 
cent  solution,  is  also  highly  recommended.  A  teaspoonful  dose  should 
be  given  immediately,  and  repeated  twice  at  intervals  of  ten  minutes. 
To  bee  stings,  apply  soda  or  dilute  ammonia. 

Poison  Ivy.  —  The  itching  and  discomfort  may  be  relieved  by  bath- 
ing the  part  in  a  mixture  of  two  teaspoons  of  carbolic  acid  (pure),  two 
tablespoons  of  glycerin,  one  half  pint  of  water  or  rose-water. 

The  Sick-room.  —  Every  boy  and  girl  ought  to  learn  something  about 
the  care  of  the  sick,  as  any  one  is  likely  to  be  called  on  to  do  this 
kind  of  work.  Good  nursing  is  often  "  half  the  battle."  The  patient 
should  have  a  cheerful  room,  but  the  bed  should  be  so  placed  that  he 
will  not  face  the  light.  Evidence  of  illness,  such  as  medicine  bottles, 
etc.,  should  be  kept  out  of  sight  so  far  as  possible.  While  it  is  not 
best  to  deceive  the  patient  as  to  his  condition,  there  should  at  all  times 
be  kept  up  an  air  of  cheerfulness  and  hope.  If  the  physician  can 
inspire  with  confidence,  and  the  nurse  give  unflagging  good  cheer,  the 
chances  of  recovery  are  greatly  improved.  Nothing  sustains  like  hope. 
Keep  the  air  of  the  room  pure.  Remove  excreta  and  everything  offen- 
sive just  as  soon  as  possible.  Do  not  rely  on  feeling  as  to  temperature, 
but  keep  a  thermometer  in  the  room. 

Sympathy  with  the  Patient.  — One  of  the  necessary  characteristics 
of  a  good  nurse  is  the  power  of  imagination.  "  How  would  I  feel,  and 


248  Physiology. 

what  would  I  like  to  have  done,  if  I  were  in  his  place?"  This  feeling 
will  lead  the  nurse  frequently  to  raise  the  patient's  head  and  turn  the 
pillow  —  the  coolness  of  the  other  side  of  the  pillow  is  refreshing;  to 
give  sips  of  cool  water ;  to  see  that  the  patient  does  not  suffer  for  want 
of  a  bath. 

Bathing  the  Sick.  —  In  bathing  a  weak  person  only  a  part  of  the 
body  should  be  moistened  at  a  time  ;  after  this  part  is  thoroughly  dried, 
another  part  may  be  washed;  it  is  often  necessary  to  do  all  this  work 
under  the  bed  clothing. 

Changing  the  Bedding.  —  In  changing  the  bed  clothing  move  the 
patient  to  one  side  of  the  bed,  push  the  clothing  along  close  to  his 
body,  and  place  the  clean  bedding  on  the  other  side ;  then  move  the 
patient  back,  remove  the  soiled  linen,  and  smooth  out  the  clean.  It  is 
often  necessary  to  warm  the  sheets  first;  they  should  be  thoroughly 
dry. 

Follow  Physician's  Directions  Faithfully.  —  Have  the  physician's 
directions  written  out  plainly,  as  they  may  be  forgotten  ;  and  if  there  is 
a  change  of  nurses  during  the  night  there  is  less  chance  of  mistake. 
Never  let  yourself  get  drowsy  when  acting  as  nurse.  Get  up  and  walk 
about,  get  a  breath  of  fresh  air,  and  if  inclined  to  be  drowsy  do  not 
allow  yourself  to  settle  back  in  an  easy-chair.  If  watching  all  night, 
take  a  good  lunch  in  the  middle  of  the  night ;  coffee  may  help  to  keep 
you  awake. 

Sweeping  the  Sick-room.  —  Do  not  allow  the  room  to  be  swept  with 
the  ordinary  broom.  The  room  should  have  rugs  that  can  be  removed 
and  shaken,  and  the  floor  wiped  with  a  moist  cloth.  If  the  room  is 
carpeted,  it  may  be  swept  with  moist  salt,  tea-grounds  or  coffee-grounds, 
sawdust,  etc.  Any  dusting  should  be  avoided ;  furniture  may  be  wiped 
with  a  damp  cloth. 

Do  not  Whisper.  —  Do  not  whisper,  as  it  disturbs  more  than  talking, 
and  also  has  an  air  of  secrecy  that  rouses  suspicion  in  the  patient. 

Food  for  the  Sick.  —  Raise  the  head  with  the  hand,  or  bolster  the 
patient  up,  when  giving  drink ;  or  if  the  patient  is  very  weak,  use  a 
rubber  or  glass  tube,  so  that  he  will  not  have  to  lift  the  head.  The 
nurse  should  know  how  to  prepare  any  food  that  may  be  needed  during 
the  night.  An  oil  stove  or  gas  stove  is  very  desirable  for  cooking,  or 
heating  poultices,  as  an  ordinary  wood  or  coal  fire  is  likely  to  die  down, 


Accidents.  249 

making  it  impossible  for  the  nurse  to  do  this  work  quickly,  as  it  is  often 
necessary  to  take  advantage  of  a  favorable  time,  as  when  the  patient 
wakens. 

Care  of  Lamps.  — Most  lamps,  when  turned  low,  give  off  a  disagree- 
able gas.  It  is  better  to  have  a  very  small  lamp  burning  at  full  height 
than  a  large  one  turned  low  ;  sperm  candles  are  recommended.  Do  not 
let  the  light  shine  into  the  patient's  face. 

To  Prevent  Sneezing.  —  It  is  well  known  that  a  sneeze  may  be  pre- 
vented by  firmly  pressing  on  the  upper  lip.  This  may  enable  a  nurse 
to  keep  from  waking  a  very  sick  patient  when,  at  a  critical  point,  sleep 
is  almost  a  question  of  life  or  death.  And  it  is  a  convenient  fact  for 
any  one  to  know.  To  prevent  coughing,  a  sip  of  cold  or  hot  water  will 
relieve  the  tickling  in  the  throat. 

Summary.  —  i .  To  stop  flow  of  blood  from  an  artery  apply  pressure 
to  the  wound,  or  between  the  wound  and  the  heart. 

2.  To  stop  flow  of  blood  from  a  vein  apply  pressure  to  the  wound  or 
beyond  the  heart. 

3.  Leaning  forward  promotes,  instead  of  checks,  nosebleed. 

4.  In  case  of  a  burn  apply  cooking  soda. 

5.  If  the  clothing  takes  fire,  lie  down  and  roll,  or  wrap  a  rug  or  shawl 
about  the  body. 

6.  If  a  person  with  clothing  on  fire  loses  his  presence  of  mind,  seize, 
throw  down,  and  wrap  in  any  woolen  clothing. 

7.  In  case  of  fainting  lay  the  body  flat  on  the  back,  loosen  clothing, 
give  fresh  air,  and  sprinkle  lightly  with  cold  water ;  if  this  does  not 
revive,  rub  the  limbs  toward  the  body,  hold  to  the  nostrils  smelling- 
salts  (or  ammonia),  and  send  for  a  physician. 

8.  Before  going  down  into  a  well,  test  the  air  by  lowering  a  lighted 
candle. 

9.  Learn  the  antidotes  of  every  poison  in  your  house  as  soon  as  it  is 
bought,  and  keep  the  antidote  at  hand. 

10.  Volunteer  to  help  take  care  of  sick  friends,  and  learn  to  do  this 
work  well. 

Questions.  —  I.  How  does  holding  up  the  wounded  part  check  bleed- 
ing ? 

2.  What  other  methods  of  resuscitation  from  drowning  are  in  use  ? 

3.  What  are  some  of  the  poisonous  substances  commonly  kept  in 
the  house  ? 

17 — PHY 


CHAPTER   XXVII. 
VACCINATION. 

Conditions  before  the  Discovery  of  Vaccination.  —  Before  the  dis- 
covery of  the  value  of  vaccination  by  Dr.  Edward  Jenner  in  1796,  small- 
pox was  so  prevalent  that  nearly  everybody  had  it,  and  many  thousands 
died  from  it  every  year,  while  other  thousands  were  left  blind  or  terribly 
scarred.  Jenner  discovered  that  persons  who  have  had  a  disease  called 
vaccinia,  or  cowpox,  are  much  less  liable  to  be  attacked  by  smallpox, 
and  that,  if  they  are  so  attacked,  the  disease  is  not  apt  to  be  severe 
or  dangerous.  Before  Jenner  made  this  discovery  any  person  who 
had  had  a  mild  attack  of  smallpox  was  considered  fortunate,  as  those 
who  have  had  the  disease  once  are  not  liable  to  have  it  again.  Since 
nearly  everybody  had  it  before  Jenner's  time,  those  who  had  had  a 
mild  attack  were  looked  upon  as  having  escaped  a  very  great  calamity. 
Nearly  everybody  in  those  days  was  scarred  more  or  less  with  small- 
pox pits.  It  was  customary  when  servants  were  employed  to  hire  none 
who  had  not  had  smallpox,  so  that  the  employer  might  not  be  put  to 
the  trouble  and  expense  of  having  to  take  care  of  a  smallpox  patient. 
So  universal  was  smallpox  and  so  terrible  were  its  results  that  it  was 
proposed,  before  Jenner  discovered  the  benefits  of  cowpox,  to  inoculate 
everybody  with  the  virus  from  a  mild  case  of  smallpox,  thus  making 
sure  that  everybody  should  have  it,  in  the  hope  that  if  the  disease 
were  thus  acquired  from  mild  cases  it  would  be  less  dangerous.  But 
Jenner's  discovery  that  cowpox  is  a  preventive  of  smallpox,  and  that 
cowpox  is  a  comparatively  harmless  disease,  soon  changed  the  whole 
condition  of  affairs.  Vaccination — that  is,  inoculation  with  the  virus 
of  cowpox,  instead  of  inoculation  with  the  virus  of  smallpox  —  became 
common. 

Value  of  Vaccination.  —The  best  medical  authority  in  every  civilized 
country  in  the  world  supports  the  proposition  that  vaccination,  more 
than  all  other  causes  combined,  accounts  for  the  fact  that  nowadays  in 
those  places  where  it  is  thoroughly  carried  out  smallpox  is  not  a  preva- 

250 


Vaccination.  251 

lent  disease,  that  very  few  deaths  result  from  it,  and  that  one  seldom 
sees  a  person  who  has  been  disfigured  by  it.  And  there  are  many 
illustrations  in  medical  literature,  both  in  olden  and  in  modern  times, 
of  the  fact  that,  when  vaccination  is  thoroughly  practiced,  smallpox 
almost  entirely  disappears,  to  break  out  again  when  vaccination  has 
been  neglected,  and  to  disappear  again  when  vaccination  is  resumed. 
London  has  furnished  such  illustrations  many  times  ;  and  the  same  has 
happened  in  many  other  cities,  such  as  Boston,  Birmingham,  Liverpool, 
and  Montreal.  In  Montreal,  for  instance,  vaccination  had  been  generally 
practiced  for  many  years,  and  there  had  been  practically  no  smallpox  in  the 
city  during  that  time.  But,  about  forty  years  ago,  many  of  the  people 
of  Montreal  refused  to  permit  their  children  to  be  vaccinated.  When, 
in  the  winter  of  1885,  a  colored  Pullman-car  porter  arrived  in  Montreal 
sick  with  smallpox,  the  disease  found  a  fertile  field  in  which  to  spread. 
Before  many  months  had  passed  thousands  of  the  people  of  Montreal 
had  had  the  disease,  three  thousand  of  them  had  died  from  it,  and  other 
thousands  were  left  maimed  and  scarred.  It  was  found,  however,  that, 
as  is  always  the  case,  very  few  of  those  who  had  been  vaccinated  were 
attacked  by  smallpox,  the  disease  taking  as  its  victims  almost  solely 
those  who  had  not  been  vaccinated. 

Harmless.  —  Vaccination  is  practically  painless  and  harmless.  The 
disease  it  causes,  cowpox,  or  vaccinia,  is  also,  compared  with  smallpox, 
a  harmless  disease.  Now  and  then  somebody  dies  after  being  vacci- 
nated. But  out  of  the  many  millions  who  are  vaccinated  every  year,  only 
a  very  few  die  as  a  remote  result  of  it.  Without  vaccination  smallpox 
would  be  prevalent  and  kill  thousands. 

Those  who  are  opposed  to  vaccination  claim  that  it  does  not  protect 
from  smallpox ;  that  it  causes  other  diseases,  such  as  tuberculosis,  or 
consumption,  scrofula,  and  tetanus,  or  lockjaw ;  that  it  is  more  dangerous 
than  smallpox,  which,  they  claim,  cannot  nowadays  become  epidemic 
because  of  the  greater  cleanliness  and  better  sanitary  conditions  which 
surround  us. 

Medical  Authority.  —  The  fact  still  remains,  however,  that  the  best 
medical  authority  in  all  civilized  countries  maintains  that  none  of  the 
claims  of  those  who  oppose  vaccination  is  founded  on  facts.  The 
best  medical  authorities  say  that  very  few,  if  any,  of  the  many  mil- 
lions who  are  vaccinated  every  year  contract  consumption  or  other 
disease  from  it.  They  show,  also,  that  many  people  die  every  year 


252  Physiology. 

from  lockjaw  as  the  result  of  infection  with  the  lockjaw  poison  absorbed 
through  scratches  no  deeper  than  those  inflicted  in  vaccinating.  They 
point  out  that  any  open  wound  may  become  infected  with  the  poison  of 
lockjaw.  Also  that,  while  it  requires  only  ten  days  for  the  poison  of 
lockjaw  to  develop,  in  most  of  the  very  few  cases  that  have  followed 
vaccination  the  disease  has  broken  out  more  than  ten  days  after  the 
vaccination  operation  was  performed.  This,  they  claim,  proves  that 
the  lockjaw  was  not  the  result  of  vaccination,  but,  as  may  happen  after 
any  other  scratch,  resulted  from  the  lockjaw  poison  finding  an  open 
wound  through  which  to  enter  the  body. 

If  proper  care  be  taken  thoroughly  to  cleanse  the  skin  before  vacci- 
nation is  performed,  if  pure  vaccine  virus  be  used,  and  if  the  little  wound 
and  the  vaccination  sore  be  kept  protected  from  infection  with  disease 
germs  from  the  air,  the  danger  from  vaccination  is  very  slight. 


CHAPTER   XXVIII. 
STIMULANTS   AND  NARCOTICS. 

Stimulants.  —  A  stimulant,  in  the  physiological  sense,  is  anything 
which  causes  an  increase  of  vital  activity  in  any  of  the  organs  of  the 
body. 

Food  is,  therefore,  a  stimulant,  because  it  increases  the  vital  activity 
of  the  organs  of  the  body.  Heat  and  cold,  in  their  first  effects,  are 
stimulants,  for  they  increase  the  vital  activity  of  the  organs  to  which 
they  are  applied.  To  illustrate,  either  heat  or  cold  will  cause  the  skin 
first  to  whiten  and  then  to  redden,  and  heat  will  cause  perspiration  to 
flow  from  the  sweat  glands. 

Alcohol,  tobacco,  opium,  morphine,  tea,  coffee  and  many  other 
things  are  also  stimulants,  because  their  first  action  after  being  taken 
into  the  body  is  to  increase  the  vital  activity  of  some  of  the  organs. 
All  the  above-mentioned  stimulants  affect,  among  other  organs,  the 
heart,  nervous  system,  and  brain  ;  and  their  effects  are  seen  first  in  these 
organs. 

Narcotics.  —  A  narcotic,  in  the  physiological  sense,  is  anything  which 
quiets  the  nervous  system  and  brain,  relieves  pain,  and  produces  sleep. 

All  narcotics  are,  in  their  first  effects,  stimulants ;  and  all  stimulants 
are,  in  their  secondary  effects,  narcotics.  So  it  may  be  said  that  stimu- 
lants are  narcotics  in  small  quantities  and  that  narcotics  are  stimulants 
in  large  quantities. 

To  illustrate  again  with  heat  and  cold :  one  of  the  effects  of  a  hot 
bath  is  to  redden  the  skin,  showing  its  stimulating  effect.  In  a  little 
while,  however,  the  whole  body  becomes  languorous  and  sleepy.  One 
of  the  effects  of  cold  is  to  redden  the  skin ;  but,  as  every  one  knows,  if 
the  cold  continue  long  enough,  the  person  becomes  drowsy  and  falls 
into  a  deep  sleep.  Where  one  *•  freezes  to  death  "  he  dies  in  a  profound 
sleep. 

Effects  of  Large  and  Small  Quantities.  —  Alcohol,  tobacco,  opium  and 
morphine  are  all  stimulants  and  all  narcotics ;  they  are  stimulants  when 

253 


254  Physiology. 


used  in  small  quantities  and  narcotics  when  used  in  large  quantities. 
Thus,  a  glass  of  wine  or  beer  sets  the  heart  to  beating  more  rapidly,  — 
the  stimulating  effect ;  but  many  glasses  of  either  will  make  him  who 
takes  them  drowsy  and  finally  put  him  into  a  drunken  sleep,  —  the 
narcotic  effect. 

We  look  upon  morphine  and  opium  as  examples  of  narcotics  because 
they  are  used  in  medicines  to  quiet  the  nervous  system,  stop  pain  and 
produce  sleep.  Yet  small  doses  of  either  have,  apparently,  only  stimu- 
lating effects,  for  the  reason  that  the  various  organs  are  able  to  resist 
the  effects  of  small  doses  and,  therefore,  do  not  become  narcotized. 

A  weary  horse  is  whipped  to  make  him  go  faster  or  pull  harder.  The 
faster  he  goes  or  the  harder  he  pulls,  the  more  tired  he  becomes,  and, 
therefore,  the  more  the  whipping  that  is  necessary  to  keep  him  going. 
The  whip  may  be  called  a  stimulant  to  the  tired  horse,  because  it  pro- 
duces an  increase  in  his  activity.  But  when  the  work  is  done,  the 
horse  is  very  tired  indeed  and  requires  a  long  rest  before  he  can  work 
well  again.  Indeed,  if  the  horse  be  compelled,  by  the  stimulating  effect 
of  the  whip,  to  run  or  pull  too  hard  and  too  long,  he  may  fall  down 
exhausted,  and  may  even  die. 

Effect  of  Continued  Use.  —  Alcohol,  tobacco,  morphine,  or  opium  are, 
like  the  whip  to  the  horse,  stimulants,  in  their  first  effects,  to  the  bodies 
of  those  who  use  them.  Like  the  whip  also,  they  will,  if  taken  in  too 
great  quantities,  bring  even  death  to  those  who  use  them. 

Even  the  most  mettlesome  and  high-spirited  horse  would,  if  the  whip 
were  constantly  used  upon  him,  get  so  used  to  it  that  he  would  not 
work  without  being  whipped.  Worse  than  that,  the  more  accustomed 
he  gets  to  the  whip,  the  more  and  the  harder  it  must  be  used  upon  him, 
until,  finally,  he  will  not  work  unless  he  be  whipped  unmercifully  all  the 
time  Such  a  horse  is  of  no  use,  and  his  cruel  master  has  spoiled  one 
of  man's  best  friends. 

Any  person  who  uses  stimulants  continuously  is  whipping  his  own 
body,  as  the  cruel  master  does  his  horse.  As  in  the  case  of  the  horse, 
the  more  the  body  is  whipped,  the  more  whipping  it  requires  to  make  it 
do  its  work,  until  it  will  not  work  at  all  unless  it  be  constantly  whipped  ; 
that  is,  constantly  under  the  influence  of  stimulants.  A  horse  that  will 
not  work  unless  it  is  constantly  whipped  is  a  poor  sort  of  a  horse.  A 
man  who  will  not,  or  cannot,  work  unless  he  is  under  the  influence  of 
stimulants  is  rather  a  poor  sort  of  a  man.  We  call  a  person  cruel  who 


Stimulants  and  Narcotics.  255 

whips  his  horse ;  a  man  is  cruel  to  himself  if  he  allows  himself  to  get 
into  such  a  condition  that  he  must  whip  his  body  with  stimulants  to 
compel  it  to  work. 

Danger  in  Forming  Habits.  —  Many  people  drink  alcoholic  liquors 
and  never  become  drunkards.  Yet  many  people  do  become  drunkards. 
In  fact,  any  person,  particularly  one  who  begins  in  youth  and  who  con- 
tinuously uses  alcoholic  liquors,  is  very  liable  indeed  to  become  a  slave 
to  drink  and  die  a  drunkard.  But  those  who  continuously  use  alcoholic 
liquors  run  serious  danger  in  other  ways,  even  though  they  may  never 
become  drunkards.  For  alcohol  goes  into  the  blood  when  it  is  taken 
into  the  stomach,  and,  therefore,  comes  in  contact  with  every  organ  of 
the  body.  The  action  of  even  small  amounts  of  alcohol  in  the  blood  is 
very  apt,  if  kept  up  for  a  long  time,  to  produce  disease  of  the  kidneys, 
liver,  stomach,  heart,  nerves  and  brain,  and  thus  cause  the  death  of 
those  who,  though  never  drunk,  are  still  slaves  to  alcohol.  These  are 
well-known  medical  facts. 

Especially  Dangerous  to  the  Young.  —  The  danger  from  stimulants  is 
especially  great  when  used  by  young  and  growing  persons.  They 
require  all  the  nervous  energy  that  their  bodies  produce  to  keep  their 
organs  growing  besides  doing  their  proper  work.  If,  therefore,  these 
organs  be  whipped  by  stimulants,  they  become  accustomed  to  them  and 
will  not,  or  cannot,  properly  work  without  them.  The  result  is  that  the 
various  organs  of  the  body,  especially  the  heart,  brain  and  nervous 
system,  do  not  develop  properly.  Worst  of  all,  there  is  the  greatest 
danger  that  such  a  person  will  become  a  slave  to  the  particular  stimu- 
lant he  may  be  using.  Thus  it  happens  that  so  many  boys  and  young 
men  become  drunkards.  They  drink  wine,  beer  and  whisky;  their 
growing  bodies  cannot  withstand  the  effects  of  the  stimulation,  and 
finally,  before  they  realize  it,  they  become  habitual  drunkards. 

Stimulants  both  Unnecessary  and  Injurious.  —  That  stimulants  are 
not  only  unnecessary  but  even  positively  injurious  is  proven  by  the  fact 
that  no  person  who  is  training  for  any  feat  of  strength,  skill,  or  endurance, 
ever  uses  any  of  them,  except,  perhaps,  a  little  weak  tea  or  coffee.  No 
one  ever  heard  of  a  person  training  for  a  football  or  a  baseball  match, 
for  a  foot-race,  for  a  rowing  match,  or  for  any  other  feat  of  strength,  skill, 
or  endurance,  ever  drinking  any  alcoholic  liquors^  or  using  tobacco, 
opium,  or  morphine.  If  they  were  good  things,  they  would  surely  be 


256  Physiology. 

used  under  these  circumstances  where  strength  and  endurance  are  re- 
quired ;  if  they  were  not  injurious,  they  would  not  be  prohibited.  The 
cigarette  is  denied  the  college  boy  who  is  training  for  the  college  game ; 
and  -if  he  breaks  the  rule,  he  is  debarred  from  the  games  because  the 
trainers  know  that  such  practice  on  his  part  weakens  his  heart  and  his 
wind,  and  that  even  one  cigarette  may  result  in  the  loss  of  a  closely 
contested  game  requiring  endurance  on  the  part  of  every  player. 

Drunkenness.  —  Too  much  alcohol  taken  into  the  body  will  make  the 
person  who  drinks  it  intoxicated  or  drunk.  He  staggers,  sees  double, 
cannot  talk  plainly,  is  foolish  and  silly  in  his  talk,  and  cannot  think 
well ;  or  he  becomes  excited  and  violent,  wants  to  fight,  imagines  that 
he  is  being  insulted,  and,  crazed  as  he  is,  sometimes  even  kills  his  best 
friend. 

After  a  while  the  drunken  man,  like  the  whipped  horse,  becomes 
exhausted.  His  muscles,  his  brain  and  his  whole  body  are  tired  out  by 
the  extra  work  the  stimulants  have  made  them  do,  and  he  falls  into  a 
drunken  sleep,  from  which  he  cannot  be  easily  aroused ;  the  narcotic 
effect  of  the  alcohol  has  shown  itself.  Indeed,  it  not  infrequently  hap- 
pens that  the  poor  drunkard  does  not  wake  up  at  all ;  but  his  heart  and 
brain,  worn  out  by  the  over-stimulation  of  the  alcohol  he  has  drunk, 
stop  working,  and  he  dies,  like  the  horse  which  has  been  lashed  beyond 
his  strength  by  his  cruel  driver. 

How  often  it  happens  that  drunken  men  commit  murder ;  many 
railroad  accidents,  bringing  death  or  terrible  injuries  to  thousands  of 
people,  have  been  due  to  the  alcohol-beclouded  brains  of  engineers, 
switchmen  and  train  dispatchers.  Our  prisons  and  jails  are  crowded 
with  convicts,  most  of  them  young  men,  who  committed  some  crime 
while  under  the  influence  of  liquor,  not  necessarily  drunk,  maybe  having 
taken  only  a  glass  or  two.  Railroad,  bank,  and  steamship  companies, 
which  are  responsible  for  lives  and  property,  have  found  by  experience 
that  it  is  not  safe  to  employ  men  who  use  liquor  habitually,  even  though 
they  never  become  intoxicated. 

Criminals.  — The  great  majority  of  our  criminals,  a  large  share  of  our 
insane,  very  many  of  our  deaths,  most  of  our  murders,  practically  all  the 
poverty,  want,  starvation  and  sickness  in  the  crowded  portions  of  our 
cities,  are  due  directly  or  indirectly  to  the  use  of  liquor. 

Many  people,  it  is  true,  drink  wine  and  beer  and  even  whisky  and 


Stimulants  and  Narcotics.  257 

never  become  drunkards.  But  any  boy  or  young  man  who  does  this 
runs  a  great  risk  of  becoming  a  slave  to  alcohol  and  ruining  his  health, 
even  if  he  does  nothing  worse. 

Tobacco.  —  Tobacco,  like  alcohol,  is  both  a  stimulant  and  a  narcotic ; 
it  affects  the  heart  and  the  nervous  system.  It  is  not  so  dangerous  to  life 
as  alcohol ;  it  does  not  fill  our  jails  and  insane  asylums  as  alcohol  does. 
But  it  is  particularly  injurious  to  the  growing  boy.  It  weakens  his  heart 
and  disturbs  his  nervous  system  and  dulls  his  brain. 

Many  boys  use  tobacco  and  think  that  it  does  them  no  harm.  But 
let  them  go  to  a  doctor  and  have  their  hearts  examined,  and  it  will  be 
found  that  that  organ  is  weaker  than  it  should  be.  If  tobacco-using 
boys  are  attacked  by  such  diseases  as  typhoid  fever  or  pneumonia,  they 
are  much  more  liable  to  die  from  heart  failure  than  if  they  had  not  used 
tobacco.  Such  boys  cannot  run  so  fast  nor  so  far,  play  marbles,  foot- 
ball, or  baseball  so  well  or  do  any  athletic  feat  so  skillfully,  as  they 
could  if  they  did  not  use  tobacco.  These  are  well-established  medical 
facts,  so  well  known  that  no  person  who  is  training  boys  or  men  for 
any  game  or  athletic  event  will  permit  any  of  those  under  his  care  to 
use  tobacco  in  any  form. 

Gcown-up  people  can  use  tobacco,  as  they  can  alcohol,  with  less  danger 
to  themselves  than  growing  boys  can.  But  even  adults  who  use  tobacco 
are  liable  to  have  weak  hearts.  In  fact,  many  men  are  refused  life  in- 
surance because  their  hearts  are  weakened  by  tobacco.  Such  men  are 
liable  to  die  from  heart  failure  if  they  run  for  a  street  car  or  make 
any  unusual  exertion,  and  pneumonia  or  any  other  severe  attack  of  ill- 
ness is  liable  to  kill  them. 

It  is  true  some  boys  use  tobacco  and  do  not  appear  to  be  injuri- 
ously affected  by  it,  and  many  men  use  it  and  die  of  old  age.  But  it 
is  the  fact,  nevertheless,  and  all  medical  men  will  bear  witness  to  the 
truth  of  it,  that  many  boys  ruin  their  health  by  using  tobacco,  and  that 
no  boy  can  be  so  strong,  so  quick,  so  skillful  at  his  games,  or  so  easily 
get  through  school,  if  he  smokes  cigarettes  or  uses  tobacco  in  anv  form. 
If  these  things  are  true,  and  they  are  true,  any  boy  who  uses  tobacco  is 
foolish. 

To  this  many  boys  will  reply,  ''  Isn^t  a  man  who  uses  tobacco  fool- 
ish?" Yes,  he  is.  But  the  danger  and  damage  from  tobacco  to  the 
growing  boy  are  greater  than  to  the  grown  man,  simply  because  the  boy 
is  growing  and  the  man  is  grown. 


258  Physiology. 

Opium.  —  Opium  is  the  dried  juice  of  a  certain  kind  of  poppy.  It 
contains  a  number  of  different  substances,  one  of  which  is  morphine,  to 
which  it  principally  owes  its  narcotic  and  stimulant  effects. 

Opium  is  used  by  the  people  of  some  nations  as  a  stimulant.  The 
Chinese,  for  instance,  are  addicted  to  the  vice,  and  many  of  our  people 
have  learned  from  them  to  smoke  opium.  Most  of  our  confirmed 
criminals,  the  poor  outcasts  who  spend  most  of  their  lives  in  prison,  are 
slaves  to  the  alcohol  and  opium  habits.  In  almost  every  Chinatown  in 
California  may  be  found  rooms  where  opium  is  smoked  by  white  people, 
and  most  of  the  poor  victims  of  this  terrible  habit  are  youths  and  young 
men.  This  is  so  because  grown  people  seldom  get  close  enough  to  the 
Chinese  to  acquire  the  habit,  only  idle  boys  and  youths  having  time  and 
inclination  to  loiter  about  the  Chinese  quarters.  Those  who  learn  to  use 
opium  soon  resort  to  crime  to  get  money  with  which  to  buy  the  deadly 
stuff,  and  soon  go  to  jail,  or  else  die.  So  that  the  white  patrons  of  the 
opium  dens  are  mostly  young  people. 

It  is  pitiable,  as  well  as  disgusting,  to  see  the  poor  fools  who  have 
become  opium  smokers.  They  have  lost  all  sense  of  shame  and  are 
content  to  associate  with  the  Chinese  in  their  dirty,  ill-smelling  houses. 
They  will  borrow  from  their  friends,  if  they  have  any,  beg  upon  the 
streets,  lie,  steal,  do  almost  anything  that  is  shameful,  in  order  to  get  a 
little  money  with  which  to  buy  opium.  They  are  pale,  trembling  and 
haggard ;  their  clothes  are  dirty  and  ragged,  and  they  soon  go  to  prison 
for  stealing,  or  as  common  vagrants,  or  they  die. 

A  certain  small  proportion  of  those  who  use  alcohol  to  excess  reform ; 
but  one  who  becomes  a  slave  to  opium  seldom  if  ever  reforms.  Like 
the  horse  that  is  used  to  the  whip,  his  organs  will  not  work  without 
being  lashed  by  the  stimulating  effects  of  the  opium.  If  he  be  deprived 
of  it,  he  cannot  eat,  and  is  nervous  and  ill-tempered.  He  cannot  go  to 
sleep  until  he  is  worn  out,  and  when  he  does  doze  off  he  has  horrible 
dreams.  He  cannot  work,  read,  or  enjoy  himself  in  any  way.  All  that 
he  thinks  about  is  opium.  He  aches  in  every  bone  and  muscle  and  nerve, 
and  his  sufferings  become  so  intense  that  he  will  stoop  to  any  meanness 
or  commit  almost  any  crime  to  obtain  the  stuff  that  has  deprived  him  of 
his  manhood  and  made  him  a  slave  to  a  more  cruel  and  unrelenting 
master  than  he  who  whips  his  poor  horse  to  death. 

Morphine.  —  Morphine  is  also  used  as  a  stimulant.  The  morphine  user 
is,  like  the  opium  user,  an  absolute  slave  to  the  habit.  Once  begun,  the 


Stimulants  and  Narcotics.  259 

use  of  the  stuff  is  very  rarely  if  ever  stopped.  Its  victims  cannot  work 
without  it  and  soon  become  so  unreliable  that  no  one  will  employ  them. 
Yet  both  opium  and  morphine  are  medicines  of  the  greatest  value 
when  used  by  physicians  for  the  cure  of  disease.  But  used  for  any 
other  purpose,  or  without  the  direction  of  a  physician,  they  are  deadly 
poisons,  sure  to  bring  those  who  use  them  to  the  lowest  depths  of 
degradation,  sure  to  make  them  criminals  and  beggars,  sure  to  send 
them  down  to  shameful  deaths  and  paupers'  graves. 


MILDER   STIMULANTS. 

Tea,  Coffee  and  Cocoa,  or  Chocolate,  are  mild  stimulants.  But  even 
they,  when  used  to  excess,  may  produce  various  nervous  troubles.  They 
act  upon  the  heart  and  nervous  system,  and,  like  all  other  stimulants, 
should  bfe  carefully  avoided  by  the  young  and  growing. 

PATENT   MEDICINES. 

There  are  many  people  who,  though  opposed  to  the  use  of  alcoholic 
beverages  of  any  kind,  do  not  hesitate  to  take,  as  medicine,  so-called 
"  bitters  "  and  other  patent  medicines,  many  of  which  contain  alcohol 
in  great  or  less  quantities,  and  which,  therefore,  are  as  intoxicating  as 
wine  or  beer  or  even  whisky.  Such  people  think  that  their  health  is 
bad ;  and  they  ascribe  to  "  the  medicine "  the  temporary  stimulating 
effect  of  the  alcohol,  which,  unknown  to  themselves,  they  are  taking. 
Unconsciously  they  take  more  and  more  of  the  stuff,  not  realizing  that 
they  are  becoming  addicted  to  the  liquor  habit  just  as  much  as  if  they 
were  drinking  any  other  alcoholic  liquors. 

Such  people  would  be  very  indignant  if  they  were  told  that  they  were 
doing  that  which  they  condemn  in  others ;  viz.,  drinking  intoxicating 
liquors.  Yet  such  is  the  fact,  and  the  worst  part  of  it  is  that  the  alcohol 
usually  found  in  such  so-called  "  medicines  "  is  of  the  cheapest,  most 
poisonous  kind,  and,  therefore,  like  the  cheapest  wines,  beers,  and 
whiskies,  is  very  destructive  to  health. 


GLOSSARY. 


Albumen  (al-bu'-meri).     The  white  of  an  egg. 

Albumin  (al-bu'-min).  A  proteid  substance,  the  chief  constituent  of 
the  body.  Its  molecule  is  highly  complex,  and  varies  widely  within 
certain  limits  in  different  organs  and  in  different  conditions. 

Albuminuria  (al-bu'-mi-nu'-rl-a}.  The  presence  of  albumin  in  the  urine, 
indicating  changes  in  the  blood  or  in  the  kidneys. 

Amylopsin  (am-i-lop'-siri).    A  ferment  said  to  exist  in  pancreatin. 

Anabolism  (an-ab'-o-lizm').  Synthetic  or  constructive  metabolism. 
Activity  and  repair  of  function  ;  opposed  to  katabolism. 

Arbor  Vitae  (ar'-ftor  m'-ie}.  A  term  applied  to  the  branched  appear- 
ance of  a  section  of  the  cerebellum. 

Argon  (ar'-f/on).  A  newly  discovered  element  similar  to  nitrogen 
(found  in  the  air). 

Arytenoid  (ar-i-tt'-noid).  Resembling  the  mouth  of  a  pitcher,  as  the 
arytenoid  cartilages  of  the  larynx. 

Atlas  (at'-las).  The  uppermost  of  the  cervical  vertebrae  (from  the 
mythical  Atlas  who  supported  the  Earth). 

Auricle  (aw'-ri-kl).  The  auricles  of  the  heart  are  the  two  cavities  be- 
tween the  veins  and  the  ventricles.  Also,  the  pinna  and  external 
meatus  of  the  ear. 

Axis  (ak'-sis).  The  second  cervical  vertebra,  on  which  the  head,  with 
the  atlas,  turns. 

Bacterium  (bak-te'-ri-um},  pi.  bacteria.  A  genus  of  microscopic  fungi 
characterized  by  short,  linear,  inflexible,  rod-like  forms  —  without 
tendency  to  unite  into  chains  or  filaments. 

Biceps  (bl'-seps}.     Biceps  brachii,  the  flexor  of  the  arm. 

Bicuspid  (bi-kus'-pid} .  Having  two  points  ;  the  bicuspid  or  premolar 
teeth ;  the  bicuspid  valve,  between  the  left  auricle  and  the  left  ven- 
tricle. 

Brachial  (bra'-ke-al  or  brak'-i-al}.    Pertaining  to  the  arm. 

261 


262  Glossary. 


Bronchus  (brong' -kits'),  pi.  bronchi.  The  two  tubes  into  which  the  tra- 
chea divides  opposite  the  third  thoracic  vertebra,  called  respectively 
the  right  and  left  bronchus. 

Caffein  (kaf-e-in).  An  alkaloid  that  occurs  in  the  leaves  and  beans  of 
the  coffee-tree,  in  Paraguay  tea,  etc. 

Canaliculus  (kan-a-lik'-u-lus*),  pi.  canaliculi.  The  crevices  extending 
from  lacunae,  through  which  nutrition  is  conveyed  to  all  parts  of 
the  bone. 

Canine  (ka-nin'  or  ka'-nlri}.  The  conical  teeth  between  the  incisors 
and  the  premolars. 

Capillary  (kap'-i-la-ri  or  ka-pil'-a-ri) .  A  minute  blood-tube  connecting 
the  smallest  ramification  of  the  arteries  with  those  of  the  veins. 

Capsule  (kap'-sul}.  A  tunic  or  bag  that  incloses  a  part  of  the  body  or 
an  organ. 

Carbohydrate  (kar-bo-hi'-drat).  An  organic  substance  containing  six 
carbon  atoms  or  some  multiple  of  six,  and  hydrogen  and  oxygen  in 
the  proportion  in  which  they  form  water;  that  is,  twice  as  many 
hydrogen  as  oxygen  atoms.  Starches,  sugars,  and  gums  are  carbo- 
hydrates. 

Cardiac  (kar'-di-ak).    Pertaining  to  the  heart. 

Carotid  (ka-rot'-id).     The  principal  right  and  left  arteries  of  the  neck. 

Carpus  (kar'-pus).     Belonging  to  the  wrist;  as  the  carpal  bones. 

Cartilage  (kar'-ti-laj*).     Gristle  of  various  kinds,  articular,  etc. 

Casein  (M'-se-w).  A  derived  albumin,  the  chief  proteid  of  milk,  pre- 
cipitated by  acids  and  by  rennet  at  40°C. 

Cecum  (se'-kum').  The  large  blind  pouch  or  cul-de-sac,  in  which  the 
large  intestine  begins. 

Centrum  (sen'-trum).  The  center  or  middle  part ;  the  body  of  a  verte- 
bra, exclusive  of  the  bases  of  the  neural  arches. 

Cerebellum  (ser-e-bel'-uin).  The  inferior  part  of  the  brain,  lying  below 
the  cerebrum. 

Cerebrum  (ser'-e-brurri}.  The  chief  portion  of  the  brain,  occupying  the 
whole  upper  part  of  the  cranium. 

Cervical  (ser'-vi-kal).     Pertaining  to  the  neck,  as  cervical  vertebrae. 

Chordae  tendineae  (kor'-de).  The  tendinous  cords  connecting  the 
fleshy  columns  of  the  heart  with  the  auriculo-ventricular  valves. 

Choroid  (ko'-roid}.  The  second  or  vascular  coat  of  the  eye,  continu- 
ous with  the  iris  in  front,  and  lying  between  the  sclerotic  and  the 
retina, 


Glossary.  263 


Chyle  (HZ).  The  milk-white  fluid  absorbed  by  the  lacteals  during  di- 
gestion. 

Chyme  (Hm).  Food  that  has  undergone  gastric  digestion,  and  has  not 
yet  been  acted  upon  by  the  biliary,  pancreatic,  and  intestinal 
secretions. 

Cilium  (siZ'-z-wm),  pi.  cilia.  The  eyelashes  ;  also  the  hair-like  appen- 
dages of  certain  epithelial  cells,  whose  function  is  to  propel  fluid 
or  particles  along  the  passages  that  they  line. 

Ciliary  (sH'-i-a-ri).  Pertaining  to  the  eyelid  or  eyelash  ;  also  by  ex- 
tension to  the  ciliary  apparatus  or  the  structure  related  to  the 
mechanism  of  accommodation.  Pertaining  to  the  cilia, 

Circumvallate  (sir-kum-nal'-at}.  Surrounded  by  a  wall  or  prominence, 
as  the  circumvallate  papillae  on  the  tongue. 

Clavicle  (klav'-i-kl).     The  collar-bone. 

Coccyx  (kok'-siks*).  The  last  bone  of  the  spinal  column,  formed  by  the 
union  of  four  rudimentary  vertebrae. 

Cochlea  (kok'-U-a).  A  cavity  of  the  internal  ear,  resembling  a  snail- 
shell. 

Conjunctiva  (kon-jungk-ti'-va).  The  mucous  membrane  covering  the 
anterior  portion  of  the  globe  of  the  eye,  reflected  on,  and  extending 
to,  the  free  edge  of  the  lids. 

Corpus  Arantii  (kor'-pus}.  The  tubercles,  one  in  the  center  of  each 
segment  of  the  semilunar  valves. 

Corpuscle  (kor'-pus-l}.  A  name  loosely  applied  to  almost  any  small, 
rounded  or  oval  body,  as  the  blood  corpuscles. 

Cortex  (kor'-teks}.  Bark.  The  outer  layer  of  gray  matter  of  the  brain  ; 
the  outer  layer,  cortical  substance,  of  the  kidney. 

Cricoid  (krl'-koid}.  Ring-shaped,  as  the  cricoid  cartilage  of  the 
larynx. 

Dentine  (den'-tiri).  The  ivory-like  substance  constituting  the  bulk  of 
the  tooth,  lying  under  the  enamel  of  the  crown  and  the  cement 
of  the  root. 

Diabetes  (di-a-be'-tez}.  The  name  of  two  different  affections,  diabetes 
mellitus,  or  persistent  glycosuria,  and  diabetes  insipidus,  or  polyu- 
ria,  both  characterized,  in  ordinary  cases,  by  an  abnormally  large 
discharge  of  urine.  The  former  is  distinguished  by  the  presence 
of  an  excessive  quantity  of  sugar  in  the  urine. 

Dialysis  (dl-al'-i-sis}.  The  operation  of  separating  crystalline  from 
colloid  substances  by  means  of  a  porous  diaphragm,  the  former 


264  Glossary. 

passing  through  the  diaphragm  into  the  pure  water  upon  which  the 
dialyzer  rests. 

Digastric  (di-gas'-trik}.  Having  two  bellies,  as  the  digastric  muscle, 
enlarged  near  each  end  and  with  a  tendon  in  the  middle. 

Duodenum  (du-o-de'-num}.  The  first  part  of  the  small  intestine,  begin- 
ning with  the  pylorus. 

Emulsion  (Je-mul'-shun).  Water  or  other  liquid  in  which  oil,  in  minute 
subdivision  of  its  particles,  is  suspended. 

Enamel  (en-am'-el}.     The  hard  covering  of  the  crown  of  a  tooth. 

Endothelium  (en-do-the'-li-um}.  The  internal  lining  membrane  of 
serous,  synovial,  and  other  internal  surfaces,  the  homolog  of  epi- 
thelium. 

Enzyme  (en'-zim).  Any  chemic  or  hydrolytic  ferment,  as  distinguished 
from  organized  ferments  such  as  yeast;  unorganized  ferment. 

Epiglottis  (ep-i-glot'-is).  A  thin  nbro-cartilaginous  valve  that  aids  in 
preventing  food  and  drink  from  passing  into  the  larynx. 

Esophagus  (e-sof-a-guti}.  The  musculo-membranous  tube  extending 
from  the  pharynx  to  the  stomach. 

Eustachian  (u-sta'-ki-an).  Eustachian  tube,  the  tube  leading  from  the 
middle  ear  to  the  pharynx. 

Facet  (fas'-et).  A  small  plane  surface.  The  articulating  surface  of  a 
bone. 

Femur  (/e'-mer).     The  thigh-bone. 

Ferment  (fer'-menf).  Any  micro-organism,  proteid,  or  other  chemic 
substance  capable  of  producing  fermentation,  i.e.,  the  oxidation 
and  disorganization  of  the  carbohydrates. 

Fibrin  (fl'-brin~).  A  native  albumen  or  proteid,  a  substance  that,  be- 
coming solid  in  shed  blood,  plasma,  and  lymph,  causes  coagulation 
of  these  fluids. 

Fibula  (fib'-u-la^).  The  smalter  or  splint  bone  in  the  outer  part  of  the 
leg,  articulating  above  with  the  tibia,  and  below  with  the  astraga- 
lus and  tibia. 

Filiform  (fil'-i-form}.     Thread-like,  as  the  filiform  papillae. 

Frontal  (fron'-tal}.     Belonging  to  the  front,  as  the  frontal  bone. 

Fungiform  (fun'-ji-form).  Having  the  form  of  a  mushroom,  as  fungi- 
form  papillae. 

Ganglion  (gang'-gli-on\  pi.  ganglions  or  ganglia.  A  separate  and  semi- 
independent  nervous  center,  communicating  with  other  ganglia  or 
nerves,  with  the  central  nervous  system,  and  peripheral  organs. 


Glossary.  265 


Gastric  (gasf'trik*).     Pertaining  to  the  stomach. 

Gelatin  (jel'-a-tin}.  An  albuminoid  substance  of  jelly-like  consistence, 
obtained  by  boiling  skin,  connective  tissue,  and  bones  of  animals 
in  water.  The  glue  of  commerce  is  an  impure  variety. 

Glosso-pharyngeal  (ylos'-o-fa-rin'-$e-al}.  Pertaining  to  the  tongue  and 
larynx. 

Gluten  (ylo'-ten).  A  substance  resembling  albumin,  and  with  which  it 
is  probably  identified  ;  it  occurs  abundantly  in  the  seeds  of  cereals. 

Glycogen  (fjli'-ko-jen}.  A  white  amorphous  powder,  tasteless  and  odor- 
less, forming  an  opalescent  solution  with  water,  and  insoluble  in 
alcohol.  It  is  commonly  known  as  animal  starch.  It  occurs  in  the 
blood  and  in  the  liver,  by  which  it  is  elaborated,  and  is  changed  by 
diastasic  ferments  into  glucose. 

Gustatory  (gus'-td-to-ri).  Pertaining  to  the  special  sense  of  taste  and 
its  organs. 

Hashish  (hash'-esJi).  A  preparation  from  Indian  hemp,  Cannabis  in- 
dica.  It  is  a  powerful  narcotic. 

Haversian  (ha-ver'-ziany.  Haversian  canal,  in  bone,  a  central  opening 
for  blood-tubes,  surrounded  by  a  number  of  concentric  rings,  or 
lamellae,  of  bone. 

Hemoglobin  (hem-o-ylo'-bin).  A  substance  existing  in  the  corpuscles  of 
the  blood,  and  to  which  their  red  color  is  due. 

Hepatic  (he-pat'-ik).     Pertaining  or  belonging  to  the  liver. 

Hilum  (hl'-lum).  A  small  pit,  scar,  or  opening  in  an  organic  structure  ; 
the  notch  on  the  internal  or  concave  border  of  the  kidney. 

Humerus  (hu'-me-rus) .     The  bone  of  the  upper  arm. 

Humor  (/m'-mor).     Any  liquid,  or  semi-liquid,  part  of  the  body. 

Hyoid  (hl'-oid}.  Having  the  form  of  the  letter  U.  The  hyoid  bone 
situated  between  the  root  of  the  tongue  and  the  larynx,  supporting 
the  tongue  and  giving  attachment  to  its  muscles. 

Hypo-glossal  (hi-po-glos'-al}.     Under  the  tongue. 

Iliac  (il'-i-ak}.  Pertaining  to  the  ilium,  or  region  of  the  flanks,  as  iliac 
artery,  vein,  etc. 

Incisor  (m-sz'-sor).     The  chisel-shaped  front  teeth. 

Inhibition  (in-hi-bish'-un}.  The  act  of  checking,  restraining,  or  sup- 
pressing ;  any  influence  that  controls,  retards,  or  restrains.  Inhib- 
itory nerves  and  centers  are  those  intermediating  a  modification, 
stoppage,  or  suppression  of  a  motor  or  secretory  act  already  in 
progress. 


18 — PHY 


266  Glossary. 

Innominate  (i-nom'-i-na£e).  Nameless  ;  a  term  applied  to  several  parts 
of  the  body  to  which  no  other  definite  name  has  been  given,  as  the 
innominate  bone,  artery,  vein,  etc. 

Invertin  (in'-ver-tin').  A  ferment  found  in  the  intestinal  juice,  and  also 
produced  by  several  species  of  plants  ;  it  converts  cane-sugar  in 
solution  into  invert  sugar. 

Jugular  (jo'-gu-lar}.     Pertaining  to  the  throat,  as  the  jugular  vein. 

Katabolism  (ka-tab'-d-lizm^.  Analytic  or  destructive  metabolism  ;  a 
physiologic  disintegration  ;  opposed  to  anabolism. 

Lacrymal  (lak'-ri-mal^.  Having  relation  to  the  organs  of  the  secretion, 
transfer,  or  excretion  of  tears. 

Lacuna  (la-ku'-na).  A  little  hollow  space  ;  especially  the  microscopic 
cavities  in  bone  occupied  by  the  bone  corpuscles,  and  communicat- 
ing with  one  another  and  with  the  haversian  canals  and  the  sur- 
faces of  the  bone  through  the  canaliculi. 

Lamella  (/a-mer-a),  pi.  lamellae.  A  thin  lamina,  scale,  or  plate  ;  of 
bone,  the  concentric  rings  surrounding  the  haversian  canals. 

Larynx  (lar'-ingks}.  The  upper  part  of  the  air  passage  between  the 
trachea  and  the  base  of  the  tongue  ;  the  voice-box. 

Legumin  (le-gu'-miri).  A  proteid  compound  in  the  seeds  of  many  plants 
belonging  to  the  natural  order  Leguminosae  (peas,  beans,  lentils, 
etc.). 

Lumbar  (lum'-bar*),  pertaining  to  the  loins,  especially  to  the  region 
about  the  loins. 

Lymphatic  (lim-fat'-ik').    Pertaining  to  lymph. 

Lymphatics  (lim-fat'-iks^.     The  tubes  that  convey  lymph. 

Lymphatic  glands.  The  glands  intercalated  in  the  pathway  of  the 
lymphatic  tubes,  through  which  lymph  is  filtered. 

Massage  (ma-sazh'}.  A  method  of  effecting  changes  in  the  local  and 
general  nutrition,  action  and  other  functions  of  the  body,  by  rub- 
bing, kneading,  and  other  manipulation  of  the  superficial  parts  of 
the  body  by  the  hand  or  an  instrument. 

Masseter  (mas'-e-ter^).  A  chewing-muscle  felt  on  the  angle  of  the 
jaw. 

Medullary  (mecT-w-Ja-n).  Pertaining  to  the  medulla,  or  marrow  ;  re- 
sembling marrow.  Also  pertaining  to  the  white  substance  of  the 
brain  contained  within  the  cortical  envelop  of  gray  matter. 

Mesenteric  (mez-en-ter'-ik).  Pertaining  to  the  mesentery,  as  artery, 
vein,  etc. 


Glossary.  267 


Mesentery  (mez'-en-fer-t).  A  fold  of  the  peritoneum  that  connects  cer- 
tain portions  of  the  intestine  with  the  dorsal  abdominal  wall. 

Metabolism  (me-tab'-d-lizm).  A  change  in  the  intimate  condition  of 
cells  ;  (1)  constructive  or  synthetic  metabolism  is  called  Anabo- 
lism  ;  in  anabolism,  the  substance  is  becoming  more  complex  and 
is  accumulating  force  ;  (2)  destructive  or  analytic  metabolism  is 
called  Katabolism  ;  in  katabolism  there  is  disintegration,  the  mate- 
rial is  becoming  less  complex,  and  there  is  loss  or  expenditure  of 
force. 

Metacarpus  (met-a-kar'-pus).     The  bones  of  the  palm  of  the  hand. 

Metatarsus  (met-a-tar'-sus}.  The  five  bones  of  the  arch  of  the  foot, 
situated  between  the  tarsus  and  the  phalanges. 

Mitral  (mi'-tral}.  Resembling  a  miter;  mitral  valve,  with  two  flaps, 
between  the  left  auricle  and  the  left  ventricle. 

Molar  (mo'-Jar).     Mill;  the  grinding-teeth. 

Mucous  (mu'-kus).     A  term  applied  to  those  tissues  that  secrete  mucus. 

Mucus  (mu'-kus}.  A  viscid  liquid  secretion  of  mucous  membranes, 
composed  essentially  of  mucin,  holding  in  suspension  desquamated 
epithelial  cells,  etc. 

Myosin  (rai'-o-sm).  A  proteid  of  the  globulin  class,  —  the  chief  proteid 
of  muscle.  Its  coagulation  after  death  causes  rigor  mortis. 

Narcosis  (nar-fco'-sis).  The  deadening  of  pain,  or  production  of  incom- 
plete or  complete  anesthesia  by  the  use  of  narcotic  agents,  such  as 
anesthetics,  opium,  and  other  drugs. 

Narcotic  (nar-kot'-ic}.     A  drug  that  produces  narcosis. 

Neural  (nu'-ral).     Pertaining  to  the  nerves. 

Neuroglia  (nu-rog'-li-a).  The  reticulated  framework  or  skeleton-work 
of  the  substance  of  the  brain  and  spinal  cord.  The  term  is  some- 
times abbreviated  to  glia. 

Nucleus  (nu'-kle-us}.  The  essential  part  of  a  typical  cell,  usually  round 
in  outline,  and  situated  in  the  center. 

Occipital  (ok-sip'-i-tal}.  Pertaining  to  the  occiput  or  back  part  of  the 
head,  as  the  occipital  bone. 

Odontoid  (o-don'-toid).  Resembling  a  tooth  ;  the  tooth-like  process 
(axis)  of  the  second  cervical  vertebra,  on  which  the  atlas  turns. 

Olfactory  (ol-fak'-to-ri*).    Pertaining  to  the  sense  of  smell. 

Osmosis  (os-mo'-sis).  That  property  by  which  liquids  and  crystalline 
substances  in  solution  pass  through  porous  septa;  endosmosis  and 
exosmosis. 


268  Glossary0 

Oxy-hemoglobin  (ok-si-hem-d-glo'-bin\  Hemoglobin  united,  molecule 
for  molecule,  with  oxygen.  It  is  the  characteristic  constituent  of 
the  red  corpuscles  to  which  the  scarlet  color  of  arterial  blood  is 
due. 

Pancreas  (pan'-kre-as').  A  large  racemose  gland  lying  transversely 
across  the  dorsal  wall  of  the  abdomen.  It  secretes  a  clear  liquid 
for  the  digestion  of  proteids,  fats,  and  carbohydrates.  The  sweet- 
bread of  animals,  vulgarly  called  the  "  belly  sweet-bread  "  in  con- 
tra-distinction  to  the  thymus,  or  true  sweet-bread. 

Pancreatin  (pan'-kre-a-tin).    The  active  element  of  the  pancreatic  juice. 

Papilla  (pa-pil'-a\  pi.  papillae.  Any  soft,  conical  elevation,  as  papillae 
of  the  dermis,  tongue,  etc. 

Papillary  (pap'-i-la-ri}.  Pertaining  to  a  papilla;  papillary  muscles,— 
the  conic  muscular  columns  of  the  heart,  to  which  the  chordae 
tendineae  are  attached. 

Parietal  (pa-ri'-e-tal}.     Pertaining  to  the  walls,  as  the  parietal  bone. 

Parotid  (pa-rot' -id}.     Near  the  ear,  as  the  parotid  salivary  glands. 

Patella  (pa-tel'-a}.     The  knee-pan. 

Peptone  (pep'-ton}.  A  proteid  body  produced  by  the  action  of  peptic 
and  pancreatic  digestion. 

Pericardium  (per-i-kar'-di-um}.  The  closed  membranous  sac  or  cover- 
ing that  envelops  the  heart. 

Periosteum  (per-i-os'-te-nm}.  A  fibrous  membrane  that  invests  the 
surfaces  of  the  bones,  except  at  the  points  of  tendinous  and  liga- 
mentary  attachments,  and  on  the  articular  surfaces  where  cartilage 
is  substituted. 

Peristaltic  (per-l-stal'-tik}.  The  peculiar  movement  of  the  intestine 
and  other  tubular  organs,  consisting  in  a  vermicular  shortening 
and  narrowing  of  the  tube,  thus  propelling  the  contents  onward. 
It  is  due  to  the  successive  contractions  of  the  bundles  of  longitudi- 
nal and  circular  muscular  fibers. 

Peritoneal  (per-i-tu-ne'-al}.     Pertaining  to  the  peritoneum. 

Peritoneum  (per-i-to-ne'-um}.  The  serous  membrane  lining  the  interior 
of  the  abdominal  cavity,  and  surrounding  the  contained  viscera. 
The  peritoneum  forms  a  closed  sac,  but  is  rendered  complex  in  its 
arrangement  by  numerous  foldings  produced  by  its  reflection -upon 
the  viscera. 

Phalanges  (fa-lan'-jez},  plural  of  phalanx  (fa'-lanyks').  Any  one  of 
the  bones  of  the  fiujrers  or  toes. 


Glossary.  269 


Phary-n  (far'-ingks}.  The  cavity  back  of  the  soft  palate.  It  commu- 
nicates anteriorly  with  the  posterior  nares,  laterally  with  the  eusta- 
chian  tubes,  ventrally  with  the  mouth,  and  posteriorly  with  the 
gullet  and  larynx. 

Plasma  (plaz'-ma).  The  original  undifferentiated  substance  of  nascent, 
living  matter.  The  fluid  part  of  the  blood  and  lymph. 

Pleura  (jjZci'-ra).  The  serous  membrane  which  envelops  the  lungs,  and 
which,  being  reflected  back,  lines  the  inner  surface  of  the  thorax. 

Plexus  (plek'-sus~).  An  aggregation  of  vessels  or  nerves  forming  an 
intricate  net-work. 

Pneumogastric  (nu-mo-gas'-trik).  Pertaining  conjointly  to  the  lungs 
and  the  stomach,  or  to  the  pneumogastric  or  vagus  nerve. 

Portal  (por'-tal}.  Pertaining  to  the  porta  (gate)  or  hilum  of  an  organ, 
especially  of  the  liver,  as  the  portal  vein. 

Postcaval  (post-ka'-val^.  Pertaining  to  the  postcava;  the  postcaval 
vein,  formerly  called  the  inferior  vena  cava,  or  vena  cava  ascendens. 

Precaval  (pre-ka'-val).  Pertaining  to  the  precava;  the  anterior  caval 
vein,  formerly  called  the  superior  vena  cava,  or  vena  cava  de- 
scendens. 

Pronation  (pro-na'-shun).     The  turning  of  the  palm  downward. 

Protoplasm  (pro'-to-plazm).  An  albuminous  substance,  ordinarily  re- 
sembling the  white  of  an  egg,  consisting  of  carbon,  oxygen,  nitro- 
gen, and  hydrogen  in  extremely  complex  and  unstable  molecular 
combination,  and  capable,  under  proper  conditions,  of  manifesting 
certain  vital  phenomena,  such  as  spontaneous  motion,  sensation, 
assimilation,  and  reproduction,  thus  constituting  the  physical  basis 
of  life  of  all  plants  and  animals. 

Ptyalin  (ti'-a-lin}.  An  amylolytic  or  diastasic  ferment  found  in  saliva, 
having  the  property  of  converting  starch  into  dextrin  and  sugar. 

Pulmonary  (pul'-mo-na-ri}.     Pertaining  to  the  lungs. 

Pylorus  (pl-lo'-rus).     The  opening  of  the  stomach  into  the  duodenum. 

Radius  (ra'-di-us).     The  outer  of  the  bones  of  the  forearm. 

Renal  (re' -rial}.     Pertaining  to  the  kidneys. 

Rennin  (ren'-in).  An  enzyme,  or  ferment,  to  whose  action  is  due  the 
curdling  or  clotting  of  milk  produced  upon  the  addition  of  ren- 
net. 

Retina  (ret'-i-na).  The  chief  and  essential  peripheral  organ  of  vision; 
the  third  or  internal  coat  or  membrane  of  the  eye,  made  up  of  the 
end  organs  or  expansion  of  the  optic  nerve  within  the  globe. 


270  Glossary. 


Sacrum  (sd'-fcrwm).    A  curved  triangular  bone,  composed  of  five  con- 
solidated vertebrae,  wedged  between  the  two  iliac  (pelvic)  bones, 

and  forming  the  dorsal  boundary  of  the  pelvis. 
Scapula  (skap'-u-la).     The  shoulder-blade. 
Sciatic  (si-at'-ik}.     Pertaining  to  the  ischium;  the  sciatic  nerve,  the 

main  nerve  of  the  thigh. 
Sclerotic  (skle-rot'-ik}.    Hard,  indurated;  pertaining  to  the  outer  coat 

of  the  eye. 
Semilunar  (sem-i-lu'-nar}.     Kesembling  a  half-moon  in  shape;  semilu- 

nar  valves,  pocket-like  valves  at  the  beginning  of  the  aorta  and 

pulmonary  artery. 
Serous  (se'-rws).     Pertaining  to,  characterized  by,  or  having  the  nature 

of,  serum. 
Serum  (se'-rwm).     The  yellowish  fluid  separating  from  the  blood  after 

the  coagulation  of  the  fibrin. 

Solar  plexus  (so'-lar).     Solar,  with  radiations  resembling  the  sun. 
Sphincter  (sfingk'-ter} .     A  muscle  surrounding  and  closing  an  orifice. 
Splenic  (splen'-ik*).     Pertaining  to  the  spleen. 
Steapsin  (step'-sin).     A  diastasic  ferment  which  causes  fats  to  combine 

with  an  additional  molecule  of  water  and  then  split  into  glycerine 

and  their  corresponding  acids. 
Sternum  (ster'-num\     The  breast-bone. 
Subclavian  (sub-kla'-vi-an').     Situated  under  the  collar-bone  ;    subcla- 

vian  artery  and  vein. 
Sublingual  (sub-ling'-gwal).     Lying  beneath  the  tongue,  as  sublingual 

gland. 
Submaxillary  (sub-mak'-si-la-ri).    Lying  beneath  the  lower  maxilla,  as 

submaxillary  salivary  gland. 

Supination  (su-pi-na'-shun*).     The  turning  of  the  palm  upward. 
Synovia  (si-no' -vi-a).     The  lubricating  liquid  secreted  by  the  synovial 

membranes  in  the  joints. 

Tarsus  (£ar'-sws).     The  instep,  consisting  of  seven  bones. 
Temporal  (tem'-po-ral).     Pertaining  to  the  temples,  as  temporal  artery, 

vein,  muscle,  etc. 
Tetanus  (tet'-a-nus*).     A  spasmodic  and  continuous  contraction  of  the 

muscles,  causing  rigidity  of  the  parts  to  which  they  are  attached. 
Thein  (the'-in}.     An  alkaloid  found  in  tea. 

Theobromin  (the-d-bro'-min~).    A  feeble  alkaloid  obtained  from  cacao- 
butter  ;  the  essential  substance  found  in  cocoa  and  chocolate. 


Glossary.  271 


Thyroid  (Mi'-roid).  Shield-shaped,  as  the  thyroid  cartilage  of  the 
larynx. 

Tibia  (tib'-i-a).  The  larger  (inner)  of  the  two  hones  of  the  leg,  com- 
monly called  the  shinbone. 

Trachea  (tra-ke'-a  or  tra'-ke-a).     The  windpipe. 

Triceps  (tri'-seps*).  Triceps  of  the  arm,  the  extensor  of  the  arm,  lying 
along  the  back  of  the  humerus. 

Tricuspid  (trl-kus'-pid) .  Having  three  cusps  or  points,  as  thetricuspid 
valve. 

Trypsin  (trip' -sin}.     The  proteolytic  ferment  of  pancreatic  juice. 

Ulna  (MJ'-na).     The  larger  (inner)  of  the  two  bones  of  the  forearm. 

Ureter  (u-re'-ter^).  The  tube  conveying  the  urine  from  the  pelvis  of  the 
kidney  to  the  bladder. 

Vaso-constrictor  (vas'-o-kon-strik'-tor).  Causing  a  constriction  of  the 
blood-vessels. 

Vaso-dilator  (vcis'-d-di-la'-tor}.  Pertaining  to  the  positive  dilating  mo- 
tility  of  the  non-striated  muscles  of  the  vascular  system. 

Vaso-motor  (vas-d-mo'-tor).  Serving  to  regulate  the  tension  of  the 
blood-vessels,  as  vaso-motor  nerves  ;  including  vaso-dilator  and 
vaso-constrictor  mechanisms. 

Ventricle  (ven'-tri-kl}.  Applied  to  certain  structures  having  a  bellied 
appearance.  The  cavities  of  the  heart  from  which  the  blood  is 
forced  out  through  the  arteries. 

Vesicle  (ves'-i-kl~).  A  small,  membranous,  bladder-like  formation,  as 
air  vesicle. 

Villus  (fliT-us),  pi.  villi.  One  of  the  numerous  minute  vascular  projec- 
tions from  the  mucous  membrane  lining  the  small  intestine,  for  ab- 
sorbing digested  food. 

Vitreous  (nT-re-ws).  Glass-like,  as  the  clear,  jelly-like,  vitreous  humor 
of  the  eye. 


INDEX. 


Absorption,  172-180. 
Accidents,  240-249. 
Accommodation,  218,  225. 

Muscle  of,  225,  226,  227. 
Adam's  apple,  237. 
Adenoids,  95. 
Air,  composition  of,  97. 

Effects  of  rebreathing,  103. 

Washed  by  rain,  114. 

Washed  by  snow,  114. 
Albinos,  125. 
Albumen,  145. 
Albuminuria,  187. 
Alcohol,  action  in  blood,  255. 

Cause  of  crime,  256. 

Cause  of  death,  256. 

Cause  of  railroad  accidents,  256. 

Compared  with  tobacco,  257. 

Effect  of  continued  use,  254. 

And  employers,  256. 

And  exhaustion,  256. 

A  narcotic,  253,  256. 

A  stimulant,  253,  254. 

Temporary  effect  of,  256. 
Alcoholic  liquors,  254,  255,  256. 

And  athletics,  255. 

Continuous  use  of,  255. 

And  criminals,  256. 

Dangerous  for  the  young,  255. 
Amylopsin,  166. 
Anatomy,  defined,  2. 
Anti-toxin,  120. 
Anvil,  235. 
Aorta,  52,  176. 
Apoplexy,  206. 


Appendix,  vermiform,  168,  169. 
Aqueous  humor,  218. 
Arteries,  action  of,  57-59. 

Blood  flow  in,  64,  65. 

Structure  of,  58,  59,  62. 
Artificial  respiration,  243,  244, 
Asiatic  cholera,  116. 
Assimilation,  185. 
Astigmatism,  229. 
Atlas,  10. 
Auricle,  48-57. 
Axis,  10. 

Bacilli,  kinds  of,  117. 
Bacteria,  118. 
Baking,  144. 
Barley,  138. 
Baseball,  194. 
Bathing,  195-197. 

The  sick,  248. 
Bee  stings,  247. 
Beef  tea,  144. 
Beer,  254,  255,  259. 
Bicycling,  195. 
Bile,  164. 
Bites  of  cats  and  dogs,  247. 

Of  snakes,  247. 
Bitters,  259. 

Black-and-blue  spots,  77. 
Bleeding,  from  arm,  240. 

From  arteries,  240. 

From  lungs,  241. 

From  neck,  240. 

From  nose,  241. 

From  stomach,  241. 

273 


Index. 


From  thigh,  240. 

From  veins,  240. 
Blind  spot,  219. 
Blister,  125. 
Blood,  74-77- 

Amount  of,  77. 

Poisoning,  116. 
Blushing,  69. 
Boats  upsetting,  245. 
Body  and  candle,  97,  98. 

And  locomotive,  102,  103. 

And  stove,  102. 
Boiling,  144. 
Boiling  water,  141. 
Bones,  5-14. 

Broken,  14,  34,  242. 

Composition  of,  12,  13. 

In  ear,  235. 

Structure  of,  12,  31. 
Boxing,  194. 
Brain,  36,  37,  198-206. 

Blood  supply  of,  206. 

Functions  located,  203. 

Rest,  205. 

Work,  205. 
Broiling,  144. 
Bronchus,  86. 
Burns,  241. 

Candle,  oxidation  of,  97,  98. 

Capillaries,  blood  flow  in,  60,  61. 

Carbohydrates,  137. 

Carbon  dioxid,  97,  103. 

Carpets,  118. 

Carpet  sweepers,  patent,  119. 

Cartilage,  10,  32,  90,  .91. 

Cecum,  168. 

Cellars,  ventilation  of,  112. 

Cells,  3. 

Of  blood,  74. 

Of  brain,  201. 

Of  epidermis,  61. 

Of  ganglions,  41,  42. 

Of  glands,  153. 


Of  lymph,  78. 

Of  muscle,  19,  20. 
Cellulose,  144. 
Cerebellum,  198,  199,  200. 

Function  of,  204. 
Cerebrospinal  nervous  system,  37. 
Cerebrum,  198. 
Cesspools,  140,  141. 
Cheese,  136. 
Chocolate,  259. 
Choking,  92. 
Choroid  coat  of  eye,  217. 
Chyle,  174,  175. 

Receptacle  of,  78. 
Chyme,  161. 

Cigarette  smoking,  256,  257. 
Ciliary  muscle,  225. 
Ciliums,  85. 
Circulation  and  clothing,  72. 

Control  of,  67. 

In  frog's  web,  60,  61. 
Clot,  80,  81. 

Coagulation  of  blood,  76,  77. 
Coccyx,  10. 
Cochlea,  235,  236. 
Cocoa,  259. 
Coffee,  253,  255,  259. 
Colds  and  deafness,  237. 

Taking,  195. 
Colon,  167,  1 68. 
Color  blindness,  221. 
Color  of  eyes,  215,  217. 
Congestion,  72. 
Conjunctiva,  215. 
Connective  tissue,  20. 
Consciousness,  201. 
Consumption,  116. 
Contagious  diseases,  119. 
Convolutions  of  brain,  198. 
Convulsions,  26. 
Cooking,  144. 
Cords,  vocal,  237,  238. 
Corn,  138. 
Cornea,  215,  217. 


Index. 


275 


Corpuscles  of  blood,  74,  75. 

Lymph,  77-81,  82. 
Coughing,  92. 
Cowpox,  250,  251. 
Cramp,  44. 
Crazy  bone,  213. 
Crossing  of  nerve  fibers,  202. 
Crystalline  lens,  218,  224,  225,  226. 
Cutaneous  sensations,  211. 

Dandruff,  125. 

Deafness  and  colds,  237. 

Defects  of  eyesight,  223-230. 

Dennis,  126. 

Desserts,  182. 

Diabetes,  187. 

Diaphragm,  83,  86,  87,  89,  176. 

Diet,  mixed,  necessity  of,  142. 

Proper,  143. 
Diffusion  of  gases,  106. 
Digestion  and  circulation,  181. 

In  the  intestine,  164. 

In  the  mouth,  146. 

And  muscular  work,  181. 

And  repose,  182. 

In  the  stomach,  156-161. 

And  study,  181. 
Digestive  tube,  146. 
Diphtheria,  116. 
Disease  germs,  116,  252. 
Dislocations,  14. 
Dropsy,  81. 

Drowning,  treatment  for,  242-245. 
Drunkards,  255. 
Drunkenness,  256. 
Duodenum,  168. 
Dura  mater,  198. 
Dust,  114-119. 

Ear,  235-237. 

Eating,  intemperance  in,  183. 

Time  of,  183. 
Eddy,  body  like,  187. 
Eggs,  136. 


Emulsion,  136,  1 66. 
Energy  from  food,  188. 

Potential,  91. 
Entire  wheat  flour,  137. 
Epidermis,  124,  125. 
Epiglottis,  156,  157. 
Equilibrium  sense,  236. 
Erysipelas,  116. 
Eustachian  tube,  235,  236. 
Excretion,  123-132,  169. 
Exercise  and  blood  flow,  70,  101. 

Forms  of,  193. 

For  general  health,  192-195. 

And  respiration,  101. 
Extensors  and  flexors,  21. 
Eye,  215-221. 
Eyes,  care  of,  230-232. 
Eyesight,  defects  of,  223-230. 

Fainting,  206,  241. 

Fans,  no. 

Far  sight,  226-228. 

Fat,  as  tissue,  184. 

Fatigue,  205. 

Fats,  absorption  of,  174,  178. 

As  food,  137. 
Fermenting,  115. 
Fibrin,  76. 
Fish,  135. 
Flavors,  234. 

Flexors  and  extensors,  21. 
P'ocus,  223. 

Natural,  225. 
Food,  134-145- 

Amount  needed,  183. 

And  foodstuffs,  134,  135. 

Need  of,  134. 

Object  of,  146. 

Preservation  of,  121. 

For  the  sick,  248. 
Football,  194. 
Foot-bath,  hot,  73. 
Foul-air  shafts,  1 10. 
Freckles,  125. 


276 


Index. 


Fruit,  139. 
Frying,  145. 
Function,  defined,  2. 
Furnace,  no. 

Ganglions,  67,  68,  201. 
Glands,  169,  170. 

And  blood  supply,  128. 

Control  of,  128,  169. 

Gastric,  159,  160. 

Intestinal,  167,  173. 

Lacrymal,  215. 

Lymphatic,  78,  79. 

Mucous,  154. 

Oil,  124,  126. 

Plan  of,  153. 

Salivary,  152-154,  165. 

Sweat,  124,  127. 
Glasses,  223,  227,  228,  229. 
Graham  flour,  138. 
Grates,  107,  in. 
Gravity  and  circulation,  71,  72. 
Grippe,  116. 
Gullet,  147,  156,  157,  158. 

Hair,  124,  126. 

Hammer,  235. 

Heart,  47-49. 

Heart -beat,  control  of,  70,  71. 

Rate  of,  47,  70. 
Heart-burn,  162. 
Heat,  conduction  of,  129. 

Convection  of,  129. 

Distribution  of,  130. 

And  exercise,  130. 

In  the  liver,  102. 

Production  of,  100. 

Radiation  of,  129. 

Source  of,  102. 
Heating,  direct,  no. 

By  hot  water,  no. 

Indirect,   1 10. 

By  steam,  1 10. 
Hemoglobin,  76,  99. 
Hemorrhage,  of  lungs,  241. 


Of  stomach,  241. 
Hiccuping,  92. 
Humor,  aqueous,  218. 

Vitreous,  218. 
Hunger,  210. 
Hygiene,  defined,  2. 
Hypermetropic  eye,  227. 
Hypodermic  injections,  82, 

Image,  on  retina,  218. 

Inflammation,  72. 

Inoculation,  250. 

Intestine,  large,  148,  167,  168,  179. 

Small,  147,  164,  1 68. 
Iris,  215,  217. 

Jenner,  Edward,  250. 

Joints,  13. 

Juice,  gastric,  159,  160. 

Intestinal,  167. 

Pancreatic,  166. 

Kidneys,  131,  132,  187. 

Labor,  division  of,  3. 
Lacrymal  secretion,  215. 
Lacteals,  173,  174,  177. 
Larynx,  237,  238. 
Lens,  crystalline,  224. 
Levers,  30,  31. 
Liver,  147,  164,  176-178. 
Lockjaw,  44,  116,  251,  252. 
Lungs,  83-88. 

Capacity  of,  94. 

Diseases  of,  1 19. 
Lymph,  77-81. 

Capillaries,  77. 

Cavities,  81. 

Spaces,  77. 

Tubes,  77. 

Veins,  175. 

Lymphatic  glands,  78,  79,  175. 
Lymphatics,  78,  174,  175. 

Mad  dog  bite,  247. 
Malaria,  116,  121. 
Mastication,  148,  154,  182. 


Index. 


277 


Measles,  116. 
Meat,  135. 

Cooking,  144. 
Meningitis,  206. 
Mesentery,  148. 
Milk,  136. 

Sterilizing,  121. 
Molds,  115. 
Morphine  (or  Morphia),  253,  254, 

258. 
Motion,  1 6,  36. 

Production  of,  100. 
Mouth,  147,  148. 

Breathing  through,  95. 
Mucous  membrane,  85. 
Mucus,  85,  154. 
Mumps,  ii 6,  154. 
Muscle  fiber,  of  heart,  19. 

Involuntary,  19. 

Plain,  19,  58,  59. 

Striated,  19. 

Voluntary,  19. 
Muscles,  16-26. 

Action  of,  17. 

And  bones,  28. 

Skeletal,  28. 

Sphincter,  161. 

Structure  of,  18,  19. 
Muscular  sense,  209. 
Mustard,  an  emetic,  246. 

Plaster,  72. 
Myopic  eye,  227. 

Nails,  127. 
Narcotics,  253-259. 
Nasal  passages,  95,  156,  157. 
Near  sight,  228-229. 

In  children,  228. 
Nerve  currents,  208. 
Nerve  endings  in  skin,  211. 
Nerves,  auditory,  200. 

Cranial,  199-202. 

Facial,  200. 

Fibers,  39. 


Function  of,  39. 

Glosso-pharyngeal,  200. 

Hypo-glossal,  201. 

Olfactory,  199. 

Optic,  199. 

Roots  of,  38,  40. 

Sciatic,  1 8,  37,  43. 

Spinal,  38. 

Structure  of,  39. 

Sympathetic,  67,  68. 

Of  taste,  233. 

Of  tongue,  233. 

Trigeminal,  199. 

Vagus,  71,  200. 
Nitrogen,  97,  135,  143. 
Nucleus,  3,  19,  61. 

Oats,  138. 

Opium,  253,  254,  255,  258. 
Organ,  defined,  2. 
Oxidation  in  the  body,  102. 
Oxygen,  97,  98,  99. 
Oxy-hemoglobin,  99. 

Pain,  209,  210. 

Palate,  156,  157. 

Pallor,  69. 

Pancreas,  147,  165,  166. 

Pancreatic  juice,  166. 

Papillas,  of  skin,  125,  126. 

Of  tongue,  233. 
Paralysis,  202. 
Patent  medicine,  259. 
Pepsin,  160. 

Peptones,  160,  162,  174,  178. 
Pericardial  fluid,  48. 
Pericardium,  48. 
Peristaltic  action,  161. 
Perspiration,  123,  124. 
Pharynx,  156. 
Physiology  defined,  2. 
Pia  mater,  198. 
Pigment,  in  skin,  125. 
Plants,  source  of  food,  190. 


278 


Index. 


Plasma,  74,  75. 
Pleura,  86. 
Pleurisy,  86. 
Pneumonia,  87,  257. 
Poison  ivy,  247. 
Poisons  and  antidotes,  246. 
Pollen,  115. 

Portal  circulation,  175,  176. 
Vein,  165,  175,  176,  177. 
Potatoes,  139. 
Potential  energy,  91. 
Presbyopia,  226. 
Pressure  sense,  212. 
Proteids,  135. 
Protoplasm,  3. 
Ptyalin,  154. 
Puff  balls,  115. 
Pulse,  47. 

Pupil  of  eye,  215,  217. 
Putrefaction,  121. 
Pylorus,  159,  161. 

Rectum,  167,  168. 

Reflex  action,  41-43. 

Rennet,  161. 

Rennin,  161. 

Respiration,  artificial,  242-245. 

Control  of,  95. 

Forced,  92. 

Movements  of,  89-91. 

Organs  of,  83. 

Rate  of,  92. 
Retina,  216,  217,  218. 
Rice,  138. 
Rickets,  14. 
Roasting,  144. 
Roots  of  nerves,  38,  40. 
Running,  33. 
Rye,  138. 

Sacrum,  10. 
Saliva,  152-154. 
Salt,  142. 
Scarlatina,  116. 


Sclerotic  coat,  215,  216,  225. 
Scrofula,  79,  251. 
Scurvy,  139. 
Secretion,  169. 

Lacrymal,  215. 
Semicircular  canals,  235,  236. 
Sensations,  cutaneous,  211. 

General,  208. 

Special,  208. 
Sense  of  equilibrium,  236. 

Muscular,  209. 

Of  pressure,  212. 

Of  temperature,  213. 
Serous  cavities,  81. 
Serum,  76,  77. 
Sick,  care  of,  247-249. 
Sight,  sense  of,  215-221. 
Skin,  absorption  by,  131. 

Color  of,  125. 

Grafting,  131. 

Nerve  endings  in,  211. 

Protection  by,  131. 

Structure  of,  124. 
Sleeplessness,  205. 
Slippers,  1 1 2. 
Smallpox,  1 1 6,  250,  251. 
Smell,  234. 
Snake  bites,  247. 
Sneezing,  92,  249. 
Sniffing,  234. 
Solar  plexus,  68. 
Sound,  236. 
Soup  making,  144. 

Value  of,  181. 
Spinal  bulb,  198,  205. 

Cord,  38,  40,  41. 

Nerves,  38. 
Spleen,  82. 
Sprains,  14. 
Standing,  32. 
Starch,  137. 
Sterilizing  milk,  121. 

Surgical  instruments,  I2O. 
Stimulants,  253-259. 


Index. 


279 


Stirrup,  235. 

Stomach,  147,  158-162,  165,  168. 

Stoves,  108,  109. 

Suffocation  in  wells,  245. 

Sugar,  137,  174. 

Sunstroke,  242. 

Swallowing,  157,  158. 

Sweat,  123. 

Amount  of,  128. 

Composition  of,  127. 

Evaporation  of,  129. 
Sweeping,  118,  119. 
Swimming,  245. 
Sympathetic  nervous  system,  67,  68. 

Tartar,  152. 
Taste,  233,  234. 
Tea,  253,  255,  259. 
Tear  gland,  215. 
Teeth,  149-152. 
Temperature  of  body,  101. 

Regulation  of,  128. 

Sense,  213. 
Tennis,  194. 
Tetanus,  44,  251. 
Thirst,  210. 

Thoracic  duct,  78,  175. 
Tissues,  denned,  2. 
Tobacco,  257. 
Tongue,  148. 
Touch,  211-213. 
Trachea,  83. 
Trypsin,  166. 
Tuberculosis,  117,  251. 
Tympanic  membrane,  235. 
Typhoid  fever,  116,  148,  257. 

Urea,  132. 
Urine,  131,  132. 

Vaccination,  250-252. 
Vaccine  virus,  250,  252. 
Vaccinia,  250,  251. 
Valves  of  heart,  49,  50,  55,  57. 


In  lymph  tubes,  78. 

In  veins,  62,  63. 

In  villuses,  173,  174. 
Vegetables,  139. 
Vegetarians,  143. 
Veins,  60-65. 

Hepatic,  176,  178. 

Iliac,  53. 

Jugular,  53,  80. 

Portal,  175-177. 

Post-caval,  51,  52,  53,  54,  80. 

Pre-caval,  52,  53,  54,  80. 

Renal,  53. 

Sub-clavian,  52,  53,  80,  175. 
Ventilation,  106,  108,  112,  113. 
Ventricle,  54,  55,  56,  57. 
Vertebra,  5-11. 
Vesicles  of  lungs,  85. 
Villuses,  173,  174. 
Vitreous  humor,  218. 
Vocal  cords,  237,  238. 
Voice,  237-239. 
Volition,  201. 

Walking,  33. 

Waste  matter,  source  of,  123. 

Water,  139. 

Drinking,  142. 

Ice,  141. 

Impurities  in,  140. 

Rain,  139. 

Well,  140. 
Wheat,  137. 

Flour,  137. 

Whisky,  255,  256,  259. 
Whooping-cough,  116. 
Wind,  107. 
Windows,  in. 
Wine,  254,  255,  256,  259. 
Wounds,  240,  247. 

X-rays,  28,  29. 

yeast,  115. 

Yellow  fever,  116,  121. 


W55976 


C  4? 


J     -A 

THE  UNIVERSITY  OF  CALIFORNIA  LIBRARY 


